If you have increased the minimum font size then try the default setting "none" as a high value can cause such issues.

• Tools > Options > Content : Fonts & Colors > Advanced > Minimum Font Size (none)

Make sure that you allow websites to choose their fonts.

• Tools > Options > Content : Fonts & Colors > Advanced > [X] "Allow pages to choose their own fonts, instead of my selections above"

Also make sure that the gfx.downloadable_fonts.enabled pref is set to true on the about:config page.

• http://kb.mozillazine.org/about:config

Thanks very much for your reply. All of the settings you suggest are indeed set the way you suggested and so the situation remains the same as described in the original post.

Turned out that this was a problem on the site - incorrect coding of the CSS caused Firefox to incorrectly render the page. Can't explain why IE, Chrome and Opera rendered the page correctly. Sorry, I don't have any additional information on the CSS coding.