August 15, 1995 Microsoft announced the release of Internet Explorer 1, which was based on a Spyglass Inc., program called Mosaic, which Microsoft licensed from the company. The browser wasn't launched with Windows 95, but was part of the Windows 95 Plus Pack.
If for any reason three of these browsers Chrome, Firefox and Safari just can't satisfy your browsing needs, you'll be glad to hear that Microsoft is going to release a public Beta version of its latest browser.
WebKit-based browsers have an excellent built-in tool for webpage debugging, Web Inspector. Basically, it's an analog of Firebug, with its own strengths and weaknesses. I've been using Web Inspector more and more lately, though one drawback bothered me a lot: It doesn't show line numbers of the CSS rules.