Dale ,that's just the difference in the default font used by either browser.
You can set them both to the same and they will look very similar.
For FF it's tools-option-content-fonts and color-advanced.
For IE8 it's tools-Internet Options-general-appearance-fonts.
Tried that, Mike. In IE8 the base fonts are set to Times New Roman for webpage fonts and Courier New for plain text font and there is nothing checked under Accessibility to ignore any webpage fonts, colors, etc. In other words, nothing changed from the default.
FF is set to the same basic fonts. Proportional is set to Serif, Serif is set to Times New Roman, San-serif is set to Arial and Monospace is set to Courier New. I do have the box checked to "Allow pages to choose their own fonts, instead of my selections above." When I uncheck that box, even TC comes out in Times New Roman.
I don't believe it's the font itself (I set my post and reply font to Verdana) but rather the way the browser renders that font. Beginning with
IE7, the browser forces anti-aliasing on most font-rendering within the browser. However Firefox, a cross-platform browser, has no native font anti-aliasing ability. And it shouldn’t since most OSs such as Windows, MacOS X, and Linux (freetype rendering) have this ability natively. Windows XP doesn’t have font-antialiasing enabled by default. However in Windows Vista, (and Windows 7 I'm sure) anti-aliasing is on by default. In MacOS and Ubuntu, it’s enabled by default. Safari on Windows copies MacOS anti-aliasing into its browser. Safari on Windows anti-aliasing looks much different than Windows (blurrier, thicker).
After some searching I found you can enable Cleartype in XP and solve the redering problem with FF.
Right-click your desktop and Select Properties
On the Appearance tab, click the Effects button
Check the box and click the list button by "Use the following method to smooth edges of screen fonts:" to ClearType. Click OK twice to save the change.