SAN FRANCISCO  The browser, that porthole onto the broad horizon of the Web, is about to get some fancy new window dressing.

Next month, after three years of development and six months of public testing, Mozilla, the insurgent browser developer that rose from the ashes of Netscape, will release Firefox 3.0. It will feature a few tricks that could change the way people organize and find the sites they visit most frequently.

Not to be outdone, Microsoft recently took the wraps off the first public test version of the latest edition of Internet Explorer, which is used by about 75 percent of all computer owners, according to Net Applications, a market share tracking firm. The finished version of Internet Explorer 8 could be released by the end of the year and is expected to have additional features.

Even Apple, which once politely kept its Safari browser within the confines of its own devices, is making a somewhat controversial push to get it onto the computers of people who use Windows PCs.