I use and recommend a simultaneous dual browser arrangement:
You can have as many browsers open as you want at the same time , without major problems.
Use FF for general & everyday surfing needs, especially to sites you don't know anything about. Depending on how many plug-in's and add-on's you "hang" onto FF, it's faster than IE, & inherently safer.
Note: Current threats include 'Antivirus 2009' or variants.
Because architecture of the Internet (notably 'Flash' scripting), vulnerabilities are readily exploited in Internet Explorer, & it is now urgent that you use Firefox with current 'NoScript' add-on, which will prevent "opacity-based attacks".
Try viewing a site with FF first, and if it does not allow the interaction you require, switch & use IE (but only when it's absolutely necessary), or to use 'Active X' or 'Flash' scripting: but use these at your own peril.
And for even greater security, without limiting functionality of either browser, get
runs your programs in an isolated space which prevents them from making permanent changes to other programs and data in your computer.
Use it for:
Secure Web Browsing: Running your Web browser under the protection of Sandboxie means that all malicious software downloaded by the browser is trapped in the sandbox and can be discarded trivially.
Enhanced Privacy: Browsing history, cookies, and cached temporary files collected while Web browsing stay in the sandbox and don't leak into Windows.
Secure E-mail: Viruses and other malicious software that might be hiding in your email can't break out of the sandbox and can't infect your real system.
Windows Stays Lean: Prevent wear-and-tear in Windows by installing software into an isolated sandbox.
Not overly difficult to use.
Recommended by Steve Gibson (Security Now & GRC).
This dual set-up will reduce web based threats to your system.