Google will release today an improved test version of its browser toolbar, whose functionality can be extended with custom buttons.

With these buttons, users can search websites directly from the new Google Toolbar 4.0 Beta. The buttons can also be used to link to websites and display syndicated feeds.

"By letting them personalise the toolbar, we're putting power in the hands of users," said Sundar Pichai, a Google product manager. Google plans to have about 50 such buttons available.

Users will be able to create their own search buttons by right-clicking on a website's search box and selecting the "generate custom search" option.

Publishers can also put a custom button on their websites for users to add to their toolbars. Developers can use an API (application programming interface) to develop custom toolbar buttons.

The custom buttons featured in Google's gallery have gone through a process of quality assurance by the Californian company, but those located elsewhere haven't, Pichai said.

The custom buttons bring to the Google toolbar the increasingly popular widget concept and strengthen the toolbar's use as a control panel for navigating the web, said Allen Weiner, a Gartner analyst.

Another new feature in Google Toolbar 4.0 Beta is the ability to create and label website bookmarks. Users need only to click on the toolbar's star icon to add a website to the toolbar's "bookmark" section, Pichai said.

Google Toolbar 4.0 Beta has an improved search box which now generates suggestions as users are typing in queries. The suggestions can be based on popular Google queries, spelling corrections and the users' own search history and bookmarks, he said.

The toolbar lets users share web pages via email or SMS (short message service) with its "send to" command. Another new feature is the ability for users to sign in to their Google account right from the toolbar, and thus access services such as Gmail.

Google Toolbar 4.0 Beta is available only for Internet Explorer 6.0 and on Windows 2000 and Windows XP. Google plans to release a version for the Firefox browser later, Pichai said.

Google would do well to add more features to the toolbar to let users tag, annotate and share web content, Gartner's Weiner said.