Admin changed something, site unusable to Firefox users

[Lynne]

Those little characters will cause lots of problems. They mean that somebody edited a file not using a plain text editor. If they show at the top of every page, then my guess is it was the config.php file that was edited incorrectly. So, go create a new config.php file using a plain text editor (notepad ++, bbedit, etc) and reupload it in place of the existing one (keep a copy of the existing one since it has the database information in it). Then see if some of your problems go away.