Following testing, Yahoo!'s is overhauling the design, content and functionality of the homepage to allow users to make it more personalised. A 'My Applications' area will give instant access to users' choice of content, programmes and sites.
Testing started with Google Mail and AOL Mail; further third parties will create programmes to sit on the applications bar.
Yahoo! is also testing a homepage news module with content from partner national newspapers The Guardian, Daily Telegraph and Daily Mail that users can click straight through to the articles.
Following the initial phase of testing, beta roll-out will take place. The timing of the full launch will depend on the results.
Yahoo! is aiming to encourage more innovation online by opening up its key technologies to third-party developers.
It is opening up its search technology for other companies to build their own search engines without investing in them from scratch.