Firefox
Firefox tabs are great. They are convenient and keep me organized. I can open several links from one website in separate tabs. I can save all of the tabs at once in the bookmarks and open them at once. Firefox was the first browser to use tabs. How ingenious is that?
The first browser plug-ins that allowed modification by the end user were offered by Firefox. However, Mozilla is not completely open source.
A big pull for me is the fact that Google browser sync works with Mozilla Firefox but not internet explorer. Google browser sync is amazing. This tool saves web history automatically… and much, much more.