A study by web-testing firm SciVisum showed one in ten websites fail to work properly on Firefox, an open source browser.

Of the 100 leading consumer sites assessed by SciVisum, 3 percent turned away non Internet Explorer users. Seven percent of sites included code recognised only by the Microsoft browser.

"Surprisingly, after all these years, users of standard-compliant browsers are still faced with sites that do not support their browser or with a link suggesting they download Internet Explorer," said Deri Jones, chief executive of SciVisum.

The report cited singled out the Odeon website, which turned away non Internet Explorer users, and the insurance site Lloyds TSB, which embedded non-standard coding recognisable only to Microsoft's product.

Government websites, including Jobcentreplus.gov.uk, also posed problems for the Firefox browser.

Firefox is an open source browser, created by the Mozilla Foundation, that has grew in popularity in part because it has less security flaws that its Microsoft competitor.

According to industry analysts, Firefox increased its market share to 8 percent in May, up from 5.59 percent in January, forcing Microsoft's Internet Explorer share down from 90.31 percent to 87.23 percent during the same period.