Abstract: A data processing system comprises a client device connectable to the internet, the client device having a web browser for accessing information via the internet; the web browser being operable to access a list providing groups of internet addresses of online retailer internet pages, each group having two or more internet addresses each relating to different respective retailers' offerings of an item for purchase, so that a current internet address being accessed by the web browser is compared with internet addresses in the list and, if the current internet address is found within one of the groups, the other internet addresses in the group are returned as alternative internet addresses relating to a current item being viewed; the web browser being operable to detect a retail price of the current item from each of the internet addresses in the group containing the current internet address; and the web browser being operable to compare the retail prices and indicate the lowest such retail price for the current

Abstract: A data processing system comprises a database configured to provide a set of internet addresses of online retailer internet pages for association with respective regular expressions each defining a code string, relative to the code representing the online retailer internet page at the respective internet address, for extracting a product price from that online retailer internet page, and a respective expected price range associated with each online retailer internet page in the set; and a testing system configured to apply the regular expression to its respective online retailer internet page to extract a product price and to detect whether the extracted product price lies within the expected price range corresponding to that online retailer internet page; the testing system being configured, in the case that the extracted product price does not lie within the expected price range, to allocate a different regular expression, from a group of candidate regular expressions, to that online retailer internet page

Abstract: A data processing system comprises a client device connectable to the internet, the client device having a web browser for accessing information via the internet; the web browser being operable to access a list providing groups of internet addresses of online retailer internet pages, each group having two or more internet addresses each relating to different respective retailers' offerings of an item for purchase, so that a current internet address being accessed by the web browser is compared with internet addresses in the list and, if the current internet address is found within one of the groups, the other internet addresses in the group are returned as alternative internet addresses relating to a current item being viewed; the web browser being operable to detect a retail price of the current item from each of the internet addresses in the group containing the current internet address; and the web browser being operable to compare the retail prices and indicate the lowest such retail price for the current