I can no longer see the Forum. It’s been like this for some time now. I am typing blind so I hope this is readable. I can get it to appear correctly by playing with the css, but that’s a bit odd. This is what it looks like to me whenver I visit.
Wild!
In your user page, there are only two options for the Theme and that’s not one of them.
Can you try another browser?
In the browser where you see this, are you using any custom style sheets or anything like that?
I wonder if you have some browser extension / add-on installed that has modified the appearance.
I wonder if you have some malware accidentally installed? Maybe do a virus check to be safe?
What browser are you using? What OS are you in?