Yahoo has started asking visitors to its Home page and other products to upgrade their web browsers to latest Firefox version. In a bid to reciprocate the favor provided by Web browser after turning Yahoo Search as its default search engine, Yahoo has took the initiative to transfer its loyal user base to the free of cost and feature rich web browser. Yahoo! has started urging visitors to its homepage to "upgrade to the new Firefox" – even when they aren't using the Mozilla browser in the first place.The message, along with a Firefox logo, has begun appearing for some users in the purple band along the top of Yahoo!'s portal pages.It's displayed when the visitor is using an outdated version of Firefox, but it also shows up for any versions of rival browsers, such as Chrome or Internet Explorer. Users of the most recent version of Firefox don't see it. Whether Firefox should be considered an "upgrade" for users of other browsers, however, is debatable.Firefox had used Google’s search engine since 2004, but when the renewal of the agreement came due this year the two companies parted ways. That honor used to go to Google, which for ten years had an exclusive arrangement with Mozilla to provide default search results for Firefox worldwide. Moz opted not to renew that contract in November, however, saying it preferred to offer Firefox users a variety of search options, depending on where they are located around the world. The partnership between Yahoo and Firefox may end up helping both — and both need help. Firefox’s user numbers have been declining for years, and Yahoo search lags behind rivals Microsoft Bing and Google Search.