More than six million people have downloaded Firefox, the open-source descendant of the Netscape browser killed off by Internet Explorer in a battle that figured large in the US anti-trust case against Microsoft.

Alternative browsers, including Opera, got a boost in October when the US security body CERT recommended a move from Explorer as a way of increasing security.

It outlined a number of "significant vulnerabilities", but the browser's greatest weakness is perhaps the fact that, as the most used browser by far, it is the one most likely to be targeted.

Firefox, which has a number of innovations including tabbed web pages, has been favourably reviewed, although it can have problems with sites making heavy use of proprietary Microsoft technology such as Active X controls.

The Mozilla organisation, which produces Firefox, has been talking of capturing 10 per cent of browser users with a year.

Meanwhile Oslo-based Opera Software has not been standing still. It announced a technology called Extensible Rendering Architecture (ERA), which allows web pages to be printed or rendered regardless of screen size.

It means that pages will not be cut off at the edges when you print them and, in combination with a zoom function, facilitates web use on small screens.

A beta of ERA is available here, and it will be included in a final version of Opera 7.60 due to be available before the new year. This has an improved user interface and voice-enabled browsing.