Internet Explorer (IE), the world's most widely used internet browser, will come under further pressure in the coming weeks following the release of updates to two free alternatives - Firefox and Opera.

The two browsers, which between them are installed on about one computer in five, will this month both release new versions which sport a range of features aimed at making the web faster, easier and more secure to use.

Firefox 3 - the third iteration of the browser made by Mozilla, an open-source software group - claims to be able to browse the web seven times faster than IE, which is made by Microsoft. A webmail page, for example, will load in 60 milliseconds, compared with 413 milliseconds on IE.

It also aims to reduce the amount of time spent using search engines by letting people find previously visited web pages by typing search terms directly into browser's address box. The browser then trawls through the pages in its memory and brings up a list of pages whose URLs contain the words. (It does not search the body text on web pages that have been visited - unlike Opera's new product.)

Among Firefox 3's other new features is the ability to choose a look and feel for the browser to match your operating system. When installed on Mac, it has a greyish tinge to suit Apple's favoured look. On a Windows machine it is blue, and on Linux a greyish orange.

It also allows users to install "add-ons" to the browser. One, for example, changes the language of the spell-checker used when you type onto web pages such as blogs. Another sets the "zoom level" for web pages, letting you increase the text size and store the preferred magnification for each website.

Tristan Nitot, the president of Mozilla Europe, said that the developers had worked closely with Google and a security organisation called StopBadware.org to enable the browser to update its security settings, and warn users off sites that looked suspicious.

"The web is central to our lives, and if your browser is slow, insecure, or tends to crash, it prevents people from having an enjoyable experience on the internet," he said.

Opera, which has a much smaller share of the market than Firefox - about 1 per cent - has meanwhile focused its efforts on synchronising web browsers on phones and PCs. Opera makes its browsing history available to other devices, which means that people can use Opera Link on their phones to search for a page that they visited last night on a PC.

"Opera 9.5 is all about the ability to take 'your web' with you wherever you go," Tatsuki Tomita, VP of consumer products at Opera, which is based in Norway, said.

A clever aspect of the updated Opera browser is that when looking for a previously visited page, a person can type directly into in the address line a word that was contained in the body text of that page and the browser will find it.

For instance, if you'd found a page of hotels.com that gave details of a hotel in Brighton, you could type Brighton into the address box and Opera would find the page. Firefox's browser would only find it if the word Brighton appeared in the title of the page or in the URL itself.

The Opera browser also has a neat feature which lets a user return to the last page he or she visited with two clicks of the mouse - dispensing with the need always to move the mouse up to the 'back' button continually.

Opera 9.5 is available for free download from today. Mozilla said that Firefox 3, which is also free, will be released next Tuesday.

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