Mozilla's Firefox has seen steady growth in market share this year, reaching more than 20% as Microsoft's Internet Explorer has fallen below 70%, a Web metrics firm said Tuesday.

As of the end of November, Firefox had a 20.78% share, while IE had fallen to 69.77%, according to Net Applications. Throughout the year, Firefox usage on the Web has grown steadily, starting in January with a 16.98% share. Internet Explorer, on the other hand, started the year with a 75.47% share.

Also showing steady growth is Apple's Safari browser, which rose to 7.13% after starting the year with a 5.82% share, Net Applications' figures showed. Google Chrome topped 1% when launched in September, and soon fell below that mark. The browser did not reach 1% again until Nov. 27, but ended the month with a 0.94% share.

Mozilla chief executive John Lilly called reaching 20% a "significant milestone" for the open source Web browser.

"It's a huge achievement by the global Mozilla community, one that just a few years ago most would have considered impossible," Lilly said in a statement.

Net Applications said Firefox's share jumped about eight-tenths of a percent in November, which is much higher than average. The major reasons were the U.S. election, which spurred usage in non-U.S. countries where Firefox is particularly popular; the Thanksgiving holiday; and the fact that November had 10 weekend days, which is more than the average 30-day month.

The above factors are significant because they led to increased residential browsing, Net Applications said. Firefox has a much larger residential share than corporate share. Firefox is expected to remain above 20% for December and beyond, Net Applications said.