Wednesday morning, an advertisement for the Google Firefox Toolbar appeared on Google's home page when viewed with Internet Explorer.
SpreadFirefox has posted a screenshot of the Web page.
Firefox is an open-source Web browser and a direct competitor of Internet Explorer. Google already partners with Firefox by offering a search-engine option for Firefox users.
"Google occasionally promotes products on its home page and is currently running a promotion for Firefox with Google Toolbar," Sony Boralv, a Google spokeswoman, told CNET News.com. "This promotion is an extension of the Firefox referrals through (the) AdSense program we announced last year. Google is promoting Firefox with Google Toolbar because tabbed browsing and safer surfing help provide our users with a great search experience."
According to Boralv, Firefox is not the first product to be promoted in this way. Google has featured Google Pack and Google Video content from the NBA and CBS.