How can I fix broken font-rendering in Safari?
If the problem persists even after attempting my first solution, try using this command in terminal:

mv ~/Library/Safari/Bookmarks.plist ~/Desktop;
mv ~/Library/Safari/TopSites.plist ~/Desktop;
rm ~/Library/Preferences/com.apple.Safari.plist;
rm ~/Library/Preferences/com.apple.Safari.plist.lockfile;
rm ~/Library/Preferences/com.apple.Safari.RSS.plist;
rm ~/Library/Caches/com.apple.Safari;
rm ~/Library/Caches/com.apple.safaridavclient;
rm ~/Library/Safari;
mv ~/Desktop ~/Library/Safari/Bookmarks.plist;
mv ~/Desktop ~/Library/Safari/TopSites.plist;


This will delete all of Safari's (possibly currupt/broken) caches and preferences. In a sense it's like reset Safari to a clean slate. This set of commands WILL backup your bookmarks and top sites, by moving them to your desktop temporarily, and then restore them after deleting the temporary files. YOU WILL LOSE ALL INFORMATION OTHER THAN TOPSITES AND BOOKMARKS.

Just incase, try manually backing up the ~/Library/Safari/Bookmarks.plist ~/Library/Safari/TopSites.plist files.