Admin changed something, site unusable to Firefox users

[MagicPID]

A fellow site administrator tried to be helpful a couple weeks ago and a long story short, the site is unusable to many people, including all that use Firefox. Before you suggest going to a backup or something, just keep in mind that wouldn't be feasible at this point. I have reuploaded all the vBulletin files (minus the custom/theme files) without luck.

Here are some of the things that are messed up.

These characters show at the top of every page for Firefox visitors.




The login screen and other screens in this format look messed up...



The post and reply screens are completely unusable. The message field does not show and well ... the picture is self explanatory.



This has drove myself as well as members of my community quite insane, except for those of us who use Chrome or other browsers. I'm unsure what to do to resolve this and I'm open to your suggestions. I fear I may have to wipe everything and start fresh, and if that's the case, your suggestions on how to proceed are appreciated.

Thank you!