For most of last year, it looked like Chrome was steadily catching up with Firefox and likely to overtake it in the first couple months of this year. But that hasn't happened; for a third straight month, Chrome has slightly declined, and Firefox has ever so slightly gained.

Across the board, the changes were small. Internet Explorer dropped 0.12 points to 52.84 percent, Firefox gained 0.04 points to 20.92 percent, and Chrome lost the same amount, 0.04 points, to 18.90 percent. Safari saw the biggest swing, gaining 0.34 points to 5.24 percent. Opera also gained slightly, picking up 0.04 points for a total of 1.71 percent.

This means that Firefox is retaining a slender lead over Google's browser. Last month we speculated that the halt in Chrome's growth might be related to Google's decision to penalize Chrome's positioning in its search results due to an advertising campaign that contravened Google's rules. The sixty day penalty will expire in the next few days, restoring Chrome's prominent positioning in Google searches.

Another factor is that the source we use, Net Applications' Net Market Share, has slightly altered the way it counts Chrome hits. Since version 13, Chrome has had a "prerendering" feature, in which it speculatively renders pages linked from the current one, so that if the user clicks one of those links, it will be able to show the destination page more quickly. In Chrome 17, this has been extended to even include pages indirectly referenced from search queries entered in the address box.

This pre-rendering tends to inflate the raw hit counts of Chrome users; visits are apparently made to sites even if the user never actually sees the resulting page. Net Applications estimates that about 4.3 percent of all Chrome hits on websites are due to this pre-rendering. The company is changing its tracker so that in future only pages that are actually seen by the user are counted, using an API offered by Google to detect the page's visibility.

In mobile, for the second time in six months, Safari has surged, apparently at Opera Mini's expense. Mobile usage is still very much in the minority; together, the mobile traffic makes up only 7.2 percent of the market.

Chrome users continue to be on the automatic upgrade treadmill. Many Firefox users still aren't. Support for version 3.6 ends in the next few weeks, with Firefox 10 deemed the Extended Support Release that will be patched for about a year. Enterprise users were quick to complain about Mozilla's rapid release strategy, and the Extended Support Release is Mozilla's answer to these users.

Anyone sticking with 3.6, pending a long-life Firefox release, should upgrade to version 10. Whether people do or not remains to be seen.

Usage of Internet Explorer 8 and 9 grew last month, with versions 6 and 7 shrinking. Microsoft is slowly starting to deliver Internet Explorer 9 as an automatic update, at least to those users who have not previously rejected its installation, but so far this policy appears to have done little to accelerate the transition to Redmond's current browser version.

Here at Ars, Chrome has cemented itself as the dominant browser.