The firm's 2009 Ecommerce Accessibility Report analysed the sites of 19 leading UK high street retailers, evaluating them against 20 best practice guidelines and awarding a score out of five for each.
John Lewis emerged as the leading retailer with a score of 74 per cent, while Boots came in second, having jumped an impressive 17 places up the table since last year's report.
The e-commerce industry in general showed slight improvements in web accessibility, raising its average score from 57 per cent last year to 62 per cent this year. This proves that stores are paying attention to basics such as descriptive page titles, headings, links and text resizing options, according to Webcredible, but many are still prioritising the addition of new features and functionality over accessibility.
Common mistakes include a lack of appropriate alt-text for images, not embedding text within images so that it can be resized properly, and a lack of skip links which can help users get to the main content more easily.
Trenton Moss, director of Webcredible, argued that a major problem for e-retailers is inconsistency, in that they apply accessibility guidelines to some pages but not others.
"There are legal requirements for the accessibility of web sites set out by the Disability Discrimination Act and, if these are not met, companies could find themselves in trouble," he explained.
"Besides, the basics of accessibility go hand-in-hand with usability and search engine optimisation, meaning that an accessible web site can help boost your online presence and sales with all user groups, not just disabled people."
Mike Carter, content management expert at WCM firm FatWire argued that content management systems can help to apply accessibility features consistently throughout a site.
"E-commerce vendors do not need to invest huge sums of money making their sites AAA accessibility compliant – any accessibility improvements no matter how small will help to improve usability, consistency and a better user experience, " he added.
Geoengineering on the sea floor near glaciers would form a new ice shelf to prevent melting
Alterations in capillary blood flow can be caused by body position change
Curiosity rover is in 'normal mode' but not transmitting scientific data back to base
NatWest outage comes a day after Barclays' IT systems shut out customers and staff