Microsoft has pushed out Internet Explorer 8.

PC arbiter Walt Mossberg, who calls the browser arguably the most important piece of software on a computer, says it's a big improvement over IE7 and a "much closer competitor to its main rival, Mozilla's Firefox."

It's more stable, more compatible with web standards, and its navigation, search, ease of use, privacy and security have been improved. It's also got a bunch of features its rivals don't such as Web Slices and Visual Search.

Mossberg, however, who's been testing the thing for months, says it's not as fast as Firefox, Safari or Chrome. In fact it can be two or three times slower, he said.

Mossberg, by the way, prefers Firefox.

IE8, Microsoft first major browser update since August of 2006, can be downloaded for free in 25 languages and works on Vista and XP at Microsoft.com/ie8.

According to Microsoft, it's supposed to block "two to four times more malware attacks than any other browser; cuts down on the time it takes to complete common tasks on the web such as searching, mapping and sharing, including navigating 15 of the 20 top worldwide sites; and blurs the lines between the services [people] use daily and the browser used to access the Internet."