A few people are noticing after installing Lion that Safari may make fonts in Web sites incorrectly, and explain some or all of the text as a series of square blocks with the capital letter A in them.
Users who have had this problem have tried resetting Safari cookies and browser caches, but have not had any chance with these measures, indicating the problem is neither with site settings nor any conflicts with the browser’s cache.
One cause for this problem is that there may be a difference between varieties of fonts you have on the system, or there may be a problem with the font cache or other system caches. Therefore, to supervise these problems you can either validate fonts using Font Book to see if there are any font conflicts, or run various cleaning routines to clear system caches.
Apple’s Font Book application can be used to supervise system fonts, including turning them on and off, as well as validating them to see if there are any conflicts. To run a Font validation, open Font Book and pick your fonts, followed by choosing Validate Fonts from the File menu. The system will check each font and explain you whether they have passed, or whether minor or major problems were found. After the custom has run, you can manage the problematic fonts by either removing them or disabling them, or otherwise fixing the specific question at hand.