In case you were wondering, Microsoft stopped making a Mac-version of Internet Explorer a long time ago. Apple provides Safari, which is great browser. There’s also:

• Camino, a Firefox-based browser with an OS X-native graphical layer: http://caminobrowser.org/. It’s fast.
• Firefox is also good, and very extensible: http://www.getfirefox.com.
• Google’s Chrome is coming along: http://www.google.com/chrome/
• Shiira is an interesting browser from Japan. Give it a try: http://shiira.jp/download/en.php