ONLINE OFFER MANAGEMENT SYSTEM FIELD OF THE INVENTION The present invention relates to an online offer management system. 5 BACKGROUND OF THE INVENTION Discount coupons (or vouchers) have been commonly used by suppliers of products or services for many years. These coupons may serve many purposes - they may be used to clear stock, to bring in new customers, or to promote the supplier's business generally. 10 With the advent of the Internet, vouchers have begun to be distributed electronically as well. For example, a consumer may sign up to be a member of a supplier's 'club', and agree to receive promotional emails, which may include discount coupons of some description. These coupons can then be printed, and taken to the supplier's shop to be redeemed. 15 In general, however, this method is slightly cumbersome for consumers, and does not fulfil all of a supplier's requirements. For example, whilst it may promote customer loyalty, it does not attract new customers, because the coupons are only sent to existing customers who have become members of the 'club'. 20 Accordingly, some voucher publishing companies offer the service of collating discount vouchers from various suppliers. Consumers can sign up with these companies, and gain access to discount vouchers from many suppliers at once. However, there is the problem that, because a supplier is dealing with a third party company, they lose some control over the 25 discounts that are being offered. In particular, the supplier does not have control over the time at which the voucher is made publicly available. Depending on the voucher publishing company's timetable, there may be a delay before an offer is made public, or the supplier may miss the voucher publishing company's deadline and be unable to publish their offer. 30 The Internet does alleviate some of these problems, in that these voucher publishing companies can make an offer available on a website at relatively short notice. However, it would still be desirable for a supplier to have greater control over the timing of the publication of their offers. 35 Another issue for suppliers is that it can be difficult to control their exposure. An offer may be made available to large numbers of potential consumers, but it is difficult to predict exactly how many of those consumers will attempt to redeem the offer. There is a risk that too many consumers will redeem the offer. It would be desirable if supplier could more easily manage their exposure in relation to a specific offer. One further issue for suppliers is that of fraud. For some offers, fraudulent use or re-use of 5 coupons may not be a problem, because the supplier has not put a limit on the number of consumers who may accept the relevant offer. However, for other offers (particularly offers where the financial transaction occurs independently of the supply of the goods or services, at a different location), there is a risk that a consumer could re-use the same voucher without even providing any additional payment. There is also the risk of employees fraudulently 10 exploiting their knowledge of the vouchers. Fraud may be a particular problem for suppliers who have multiple stores, and it would of course be desirable to reduce the incidence of fraud in the context of the use of discount vouchers. It is an object of the present invention to reduce or ameliorate some or all of the above 15 difficulties, or at least to provide an alternative to existing methods of distributing supplier offers. SUMMARY OF THE INVENTION According to a first aspect of the present invention, there is provided a computer-implemented 20 method of managing supplier offers comprising: associating a user with a supplier; receiving, via a computer network, user identification for the user; receiving from the user, via the computer network, details of an offer made by the supplier which can be accepted by multiple consumers; 25 displaying the offer to a consumer; receiving a consumer request to accept the offer; and distributing a coupon to the consumer, to allow the consumer to redeem the offer from the supplier. 30 The coupon may be distributed to the consumer using a variety of means. In some embodiments, the coupon is an electronic coupon which may be distributed by a short message service (SMS) message to a mobile telephone. The SMS message may be taken and shown to the supplier, in order to redeem the offer. 35 The vouchers will typically involve a payment from the consumer to the supplier (e.g. a "Hot Price" or 10% off voucher, or a two-for-one deal). In some embodiments, a "Buy It Now" 2 function may be provided, wherein the consumer is able to pay for the goods or services online, and then visit the supplier at a later date to redeem the purchased goods or services. If, for example, a "Buy It Now" offer is accepted by many consumers, one advantage for a 5 supplier is that they immediately can gain access to the funds used to purchase the "Buy It Now" goods or services. If large numbers of consumers purchase goods or services on a "Buy It Now" basis, this may help to justify the discount, as a critical mass of consumers may be attained. Furthermore, the supplier immediately gains access to a large amount of funds. However, there is the disadvantage that the supplier may actually expose themselves to a 10 larger liability than they wish - they may spend several future months redeeming vouchers for consumers, without obtaining the further funds. Furthermore, because the goods or services were originally sold at a discounted price, the supplier did not make as much money from their sale as they otherwise would have. 15 Accordingly, the present invention may further comprise allowing a user to specify a predetermined number of consumers who can accept the offer. To implement this, a predetermined number of redemption codes may be assigned, which can be distributed with the coupon. Only coupons having one of these valid coupons may be redeemed. In this way, the exposure of the supplier is limited. 20 However, another issue (which increases in importance for "Buy It Now" offers), is that the supplier receives no further payment at the time of supplying the goods or services. Accordingly, it can be important that the supplier is able to verify whether a coupon code is valid, or whether (for example) it has already been redeemed. Therefore, the present invention 25 may further comprise receiving an indication that a consumer is attempting to redeem the coupon, and verifying the coupon code. Typically, multiple offers from different suppliers will be displayed to the consumer at once, and the consumer can choose which of those offers to accept. 30 The present invention may further comprise presenting, to the user, a calculation of the commercial effect of the acceptance of the offer by a specified number of consumers. The user can therefore obtain an estimate of the likely profit, or likely amount lost as an 'advertising cost'. 35 The method may further comprise associating a supplier style with the supplier, and displaying the offer to the consumer using the supplier style. 3 In a second aspect of the present invention, there is provided an offer management server comprising: a network interface, for transmitting and receiving over a computer network; and 5 a processor adapted to perform the method of the first aspect of the present invention. In a third aspect of the present invention, there is provided a method of publishing an offer, comprising: providing a user identification via a computer network; 10 transmitting, via the computer network, details of an offer which can be accepted by multiple consumers, wherein acceptance of the offer by a consumer results in the distribution of a coupon to the consumer; and fulfilling the offer upon receipt of the coupon from the consumer. 15 In a fourth aspect of the present invention, there is provided a method of distributing a supplier offer, comprising: displaying the offer to a consumer; receiving a consumer request to accept the offer; and transmitting a coupon to the consumer via a short message service (SMS) message, to 20 allow the consumer to redeem the offer from the supplier. According to a further aspect of the present invention, there is provided a computer program product, comprising a computer usable medium having a computer readable program code embodied therein, said computer readable program code adapted to be executed to implement 25 the steps of the method of the first aspect of the present invention. According to a further aspect of the present invention, there is provided an apparatus adapted to perform the preceding method. Yet further aspects of the present invention will be revealed throughout this specification. 30 A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate by way of example the principles of the invention. While the invention is described in connection with such embodiments, it should be understood that the invention is not limited to any embodiment. On the contrary, the scope of 35 the invention is limited only by the appended claims and the invention encompasses numerous alternatives, modifications and equivalents. For the purpose of example, numerous 4 specific details are set forth in the following description in order to provide a thorough understanding of the present invention. The present invention may be practiced according to the claims without some or all of these 5 specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the present invention is not unnecessarily obscured. BRIEF DESCRIPTION OF THE DRAWINGS 10 An illustrative embodiment of the present invention will be discussed with reference to the accompanying drawings wherein: FIGURE 1 is a flow chart depicting a method according to one embodiment of the first aspect of the present invention; 15 FIGURES 2 to 5 are screenshots from a website implementing the method of claim 1; FIGURE 6 is a schematic diagram of a computer architecture that may be used to implement a server according to an embodiment of the present invention; and 20 FIGURE 7 is a flow chart depicting a method according to one embodiment of the third aspect of the present invention. DETAILED DESCRIPTION 25 This embodiment of the present invention is implemented by a computer server which is adapted to provide a website accessible by Internet-enabled devices. For convenience, the operation of the server will hereafter often be referred to in the context of the operation of the website. Consumers and suppliers (or supplier representatives) can sign up to the website, to begin making use of its functionality, and create a user profile (including a user identifier, and 30 typically a password). Once a user has created a user profile, they can begin to access functionality of the website provided for consumers. However, if they wish to access specific functionality for suppliers, enabling them to create and manage offers, then this embodiment of the invention first 35 requires them to authenticate themselves as being associated with a particular supplier. This may simply involve providing the name and address of the supplier's place of business, and an email address to which the website can send an email for confirmation and/or 5 authentication. It may also involve a check of the supplier's business number or other government or third party details for verification that the user is associated with a legitimate supplier. 5 Figure 1 depicts the operation of the server according to this embodiment of the present invention. Once the user has been associated with a particular supplier 10, they are able to login 20 as required, by providing identification details (typically just a user name and password). They can then create and manage offers from the supplier, which are made available to multiple consumers who are also members of the website. 10 Figure 2 depicts an example screen which may be displayed on the website to a user who has been associated with a supplier. A user can create a new offer, to be displayed to consumers, by clicking on the "Create New Offer" button 31. This brings up a new page, as shown in Figure 3, where the user can input the offer text "e.g. 20% offer all stock", or "Buy 2 15 products, get one free". They can also indicate whether consumers are intended to pay in full at the time of accepting the offer on the website, buy indicating whether the offer is a "Buy It Now" offer, by selecting an appropriate radio button 33. Further details of "Buy It Now" offers, as 20 implemented by the present invention, will be discussed later. The user may also enter a maximum number of sales 34 that may be accepted in relation to this offer, and may indicate the types of coupons and distribution methods 35 which consumers may present to redeem this offer (e.g. SMS, email, printed paper). By default, 25 there will be no maximum number of sales, and all types of coupon distribution options will be allowed. In some embodiments, any value may be entered in the maximum sales field 34, whilst in other embodiments the maximum sales field 34 may only accept values within a particular range (e.g. I - 5,000). Furthermore, the user may input a date range for which the offer is valid, in date fields 36. 30 The details of the offer may vary quite widely within the scope of the present invention, and subject to the user preferences. For example, in some cases, an offer may provide 90% off for the first ten sold, 80% off for the next twenty sold, 60% off for the next thirty sold, etc. This provides some urgency for the consumer to buy early. 35 6 Once all details of the offer are entered, the user can click "Submit" to make the offer live and available to consumers. The details of the offer are received 30 by the website, and can then be displayed 40 to consumers. 5 Consumers who are members of the website can log in and view available offers. In this embodiment, offers are displayed 40 as icons or stubs 42 (e.g. Offer Stub 1 to Offer Stub 15 as shown in Figure 4). The user can click on one of these stubs to proceed to the next page, shown in Figure 5, which displays more details about the offer. 10 On the page shown in Figure 5, details of the supplier 45 are also displayed to the user (e.g. supplier logo, address and a link to the supplier's website). A map 46 showing locations of the supplier's stores is also displayed. This supplier information 45 and map 46 may assist the user in deciding whether to accept an offer, and (if so) where to go to redeem the offer. 15 If a user wishes to accept the offer 50, they can do so by clicking on a button (62, 64, 68) requesting that a coupon be distributed to them. The distribution options include a short message service (SMS) message (requested by clicking button 62), email (requested by clicking button 64) or simply a printed distribution method (requested by clicking button 68). Furthermore, a consumer may share the offer with other users of the website by clicking on 20 the share button 66. Once a user has accepted the offer in this way, the website (i.e. the server) distributes 60 a coupon to the consumer. This may be as simple as sending an SMS message to the consumer, which can be received by a mobile telephone device. Similarly, if requested, the server could 25 send an email to the consumer. Once the user has received the coupon (e.g. in the form of an SMS message), they can take this to the supplier in order to receive the goods and or services that are to be provided under the offer. This may be as simple as showing them, on their mobile telephone device, the SMS 30 message that they received from the supplier. If any further payment is required (i.e. if payment was not made at the time of accepting the offer on the website), then it can be made directly to the supplier at this time. However, this embodiment of the present invention allows the consumer to pay for the goods 35 or services at the time of accepting the offer on the website. There are various conventional payment processing applications that can be used in accordance with the present invention, 7 including online payment by credit card or direct debit, and the present invention is not limited to the use of any specific payment means. However, processing payment prior to purchase does raise some additional issues. In 5 particular, it increases the importance of the security of the coupon that is distributed - for example, it is increasingly important that a coupon cannot be redeemed more than once, because the consumer has already paid in full and no further payment is made at the time of receiving the goods or services from the supplier. 10 This embodiment addresses this issue in the following ways. Firstly, it allows a consumer to enter a maximum number of sales that they are prepared to make for this particular offer, by entering a figure in the Max Sales field 34 shown in Figure 3, which provides a predetermined number of consumers who can accept the offer. If a user inputs a maximum of (say) 100 sales, then the website will create 100 coupon codes which are known to the supplier, and can be 15 distributed to consumers upon receiving their payment. However, there is still the issue that the same coupon code could be presented to the supplier on multiple occasions, which can become a particular problem if the supplier has multiple stores in different locations. There is also the possibility of employee fraud - an employee, 20 having access to the codes, could fraudulently redeem a coupon knowing that is not genuine (or was not even presented to them). Accordingly, this embodiment of the present invention provides a verification service which can be used by the supplier to verify that a coupon is genuine, and to either prevent employee 25 fraud or to help identify it after it occurs. In this embodiment, each coupon is issued with both a coupon code (known to the supplier) and security code, which is distributed to the consumer and is not known to the supplier until the genuine coupon is presented at the supplier's retail outlet. 30 For example, for an offer with a maximum of 100 sales, the following codes may be assigned, as shown in Table 1: Coupon Code Security Code 001 BXS14Y 002 A47J6 8 100 SSPT31 Table I When the genuine coupon is presented at a retail outlet, a store employee can note the coupon 5 code as well as the associated security code. They can immediately access the website described above, using a computer available at the retail outlet (or potentially any other Internet-enabled device). They can then input the coupon code and the security code. Upon receipt of the verification request, the website will be able to verify the coupon 80, and specifically: 10 * verify that the coupon code has actually been issued to a consumer (if a code has note yet been issued at all, it can be determined that the coupon is not genuine); e verify that the coupon code has not previously been redeemed; and " verify that the security code presented with the coupon is correct (i.e. that this 15 is the consumer to whom the code was actually issued). A further feature of the present invention is that there is a calculator provided to enable the user (being associated with a supplier) to estimate the profit/expenditure associated with a particular offer. A user may input the recommended retail price (RRP) of a product or service, 20 the discounted price under the offer, and the number of offers they expect might be accepted. The website will then calculate the expected total income received, as well as the deficit compared to the recommended retail price and any commissioned received by the operators of the website. An example is as follows: 25 Calculation Input RRP of Product: $100 Cost of Product: $60 Discounted Offer Price: $70 No of Sales: 1,000 30 Calculation Output Value of Goods (RRP): $100,000 Value of Goods (Cost): $60,000 Value Obtained: $70,000 35 Website Commission: $1,000 9 Profit/Loss (over Cost): $9,000 Profit/Loss (compared to RRP): -$31,000 5 For more complicated offers having variable discount schemes (e.g. offers which provide different discounts depending on how early the consumer purchases the product, such as an 80% discount for the first twenty purchases but only 60% off for subsequent purchases), the calculation above preferably takes this into account, to provide the user with an accurate picture of the commercial effect of the offer. 10 Some suppliers may wish to have their products advertised under their own brand, using their own style. Accordingly, a "white labelling" function may be provided, whereby an offer is displayed using a supplier-specified style, which may predominantly feature the supplier's branding. 15 Furthermore, a "white labelling" function may be supplied for other parties (other than suppliers), such as media outfits who would like to use the functionality of the website of this embodiment of the present invention. This is particularly useful for other parties with high traffic websites. In this case, offers can be displayed using the style of the third party website, 20 whilst accessing the server of the website of the present invention, to provide functionality. The offers may only be offers which are in some way associated with the third party - e.g. if the third party is independently providing advertising or promotional services to the supplier of the offer. For example, these offers may be advertised on the third party website, with a link on the third party's website to a page detailing the offer (and allowing acceptance of the 25 offer) on the website of the present invention. However, because the offer is displayed by the website using the third party styling, the involvement of the website of the present invention will be substantially transparent to the consumer. Turning again to Figure 2, suppliers may use mailing list functionality 38 to alert consumers 30 to the existence of particular offers. Once alerted, the user can then log in to the website to accept the offer and receive a coupon via their preferred distribution method. As previously described, the present invention may be implemented using a programmable device such as a computer server 130 connected to a computer network, and in particular the 35 Internet. Figure 6 schematically and generally depicts exemplary architecture that may be used in a server 130 for implementing the method according to an embodiment of the present invention. A central processing unit (CPU) 131, containing an Input/Output Interface 133, an 10 Arithmetic and Logic Unit (ALU) 132 and a Control Unit and Program Counter element 134 is in communication with input and output devices through the Input/Output Interface 133, and a memory 135. The Input/Output Interface 133 may also comprise a network interface. The present invention can be implemented using a software application for execution on the 5 server 130. Figure 7 depicts a method according to an embodiment of the third aspect of the present invention, generally performed by a supplier utilising the above described website. To use the website, a user (associated with the supplier) submits a user identification 210 to log in to the 10 website. They then transmit offer details 220, as previously described with reference to Figures 2 and 3. A consumer can then access the website to obtain a coupon, which the supplier will then receive 230 when the consumer proceeds to one of the supplier's retail outlets. In the embodiment shown in Figure 7, the supplier then requests verification of the coupon 240 from the website. The supplier may access the website using a conventional 15 Internet browser, or alternatively their point-of-sale software may be adapted to interact with the website. Upon receiving verification of the coupon 250, the supplier then fulfils the offer 260 by supplying the relevant goods or services. Those of skill in the art would understand that information and signals may be represented 20 using any of a variety of technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 25 Those of skill in the art would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described 30 above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. 35 The steps of a method or algorithm described in connection with the embodiments disclosed herein may in some cases be performed in different orders. They may also be embodied 11 directly in hardware, in a software module executed by a processor, or in a combination of the two. For a hardware implementation, processing may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable 5 gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. Software modules, also known as computer programs, computer codes, or instructions, may contain a number a number of source code or object code segments or instructions, and may reside in any computer readable medium such as a RAM memory, flash memory, ROM 10 memory, EPROM memory, registers, hard disk, a removable disk, a CD-ROM, a DVD-ROM or any other form of computer readable medium. In the alternative, the computer readable medium may be integral to the processor. The processor and the computer readable medium may reside in an ASIC or related device. The software codes may be stored in a memory unit and executed by a processor. The memory unit may be implemented within the processor or 15 external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art. Throughout the specification and the claims that follow, unless the context requires otherwise, the words "comprise" and "include" and variations such as "comprising" and "including" will 20 be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common 25 general knowledge. It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted 30 herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims. 12