Thousands of businesses face potentially huge costs to rewrite their external and internal websites to take advantage of new standards-based browsers such as Microsoft's Internet Explorer 9 (IE9), which is out today in its final release candidate form.
Mark Quirk, web product manager in Microsoft's development platform group, told Computer Weekly that the latest, more standards-conformant, browsers were likely to "break" older websites, many of which do not conform to the latest World Wide Web Consortium (W3C) standards for web sites.
Tom Hopkins, managing consultant with EMC Consulting, a Microsoft partner, added: "All it means is that some parts of the website may not display correctly. A complete fail is very unlikely."
But Computer Weekly has found evidence that more than 1,000 popular UK websites may break when users with IE8 or IE9 browsers visit them. These include the websites of the BBC, British Airways, and the National Lottery. It is not clear if other browsers also break the websites in question, but it seems possible.
Some company web sites would have to be redeveloped from scratch because they did not conform to W3C standards, but developers who followed the standards would be able to upgrade their clients' sites relatively easily, Hopkins said.
Microsoft has known about the so-called compatibility issue since June 2008. It warned software developers to use an HTML meta tag (IE=EmulateIE7) that instructs the browser to render incompatible websites using IE7 code.
Microsoft still recommends that website developers use this utility, and ensure that the browser reads it before it reads any other code about the website. This is also true for internal websites.
Companies could choose whether to upgrade their websites to work better with the latest browsers, to emulate older versions, or to spend the money on other things, Quirk said.
Moving to standards would include using HTML4 now and HTML5 soon for coding, and Cascading Style Sheets (CSS) rather than nested tables to organise page elements, he said.
Hopkins said web site developers were led by what their clients asked for. Usually they specified compatibility with a range of browsers, but not all, he said. There were now "hundreds" of different browsers.
Hopkins said website developers tended to use what worked, and this often put their clients' websites ahead of the prevailing standard. In time this could lead to compatibility problems, he said.
Quirk said browser developers could either wait for the standards to be published, or they could introduce new features and functions as they emerged. This risked a degree of future incompatibility if the final standards did not incorporate them.
He said Microsoft based its product development on 1,000 top websites. It trawled the websites to see how it worked, then did a statistical analysis to see where to trade off features and functions to optimise the browser for most of the sites.
In at least one case Microsoft had found a standard feature that broke a lot of websites. Subsequent talks with other browser developers had led to the standard being changed, he said.
Companies that are worried about their internal web sites - those that sit behind the corporate firewall - could volunteer to join Microsoft's pre-release programme, said Quirk. This would allow website developers early insights into how the supplier's new browsers would work with their sites.
He said there was lots of technical help available to software developers via the TechNet website, and firms could also use consultancies. There was also advice on how to move towards web standards. Direct help from Microsoft was available through its consultancy service.
Browsers are converging on the W3C standards, Quirk said, adding IE9 was the most up to date and most standards-based browser. However, he could not say when the W3C would publish a new standard.
Hopkins noted that there was a also a proliferation of browsers with the launch of HP's TouchPad.
Quirk said more than 25 million people had downloaded a pre-release version of IE9. It gave better protection against malware, made websites and elements such as video and audio run faster, cut the amount of screen space devoted to the browser, and worked more like a Windows application, he said.
"They integrate with the taskbar inside Windows. "It's a fundamental part of what IE9 provides," he said.
Microsoft's Internet Explorer has previously been the subject of an anti-trust case from the European Commission over bundling the product with the Windows operating system.