[Lynne]

I don't see it as an unregistered user. So my guess is you have some condition in there that shows some code to only certain usergroups and the html for that code is wrong.

Whoever is doing your site is definitely doing some wrong things:

<meta name="keywords" content="<meta name="keywords" content="Xbox,Mac,PC,Cheats,Hacking,Mods,Halo,Cod,Call of duty black ops,Cod black ops,black ops,Homefronts,hacking,hack,xboxgamershq,xboxgamershq.com,glitching,wii,psp,psp mods,wii mods,psp hacks,free,give aways,youtube,Moderen warfare,Arcade,GTA,Minecraft,Grapchis,Ipod Tuts,ipod Downloads,Moderen warfare 2,Forza,Forza 2,Forza 3,console,PS3,XGHQ,XGheadquarters,xboxgaersHQ" />         
<meta name="description" content="<meta name="description" content="Welcome to XboxGamersHQ, Your place for Hacks,Mods, Lobbies and anything Gaming!" /> 

and
<meta property="og:description" content="<meta name="description" content="Welcome to XboxGamersHQ, Your place for Hacks,Mods, Lobbies and anything Gaming!" /> 

Those lines could be the issue but I'm just not seeing it in firefox.