Reading websites with horrible fonts

My company provides access to Safari. Safari default fonts are not very readable with Firefox with Linux. I could opt to override all fonts in Firefox settings but this is not very desirable. Instead I just "disable styles" (Ctrl-Shift-S) using the Webdeveloper extension. I find that this simple trick makes many sites much more readable. Now if only I could figure out how to disable styles for only specific sites, life would be heaven :-).