Problem with default fonts.

If you're using Safari, open Preferences, then click the Appearance tab. Change your fonts from there. Default standard font is Trebuchet MS size 14, default fixed-width font is Courier size 13, and default encoding is Western (ISO Latin 1).

If you're using Firefox, it's almost the same. Open Preferences, then click the Content tab. Default font is Times size 16.

In Chrome, open Preferences then click the Under the Hood tab. Underneath Web Content, click Change font settings. Default serif font is Times New Roman size 16, sans-serif is Helvetica size 16, fixed-width is Courier size 13, and default encoding is Western (ISO-8859-1).

If none of these help or are too complicated, you can reset the settings to default in any of these browsers. You'll lose any custom settings, but you'll most likely get your fonts back.