Hey Epic,
There is no CSS on UnrealEngine.com what is going on?
It looks normal to me, which browser are you using?
Might be worth flushing your browser cache, just in case. That sometimes causes these issues. 
Edit: actually it is slightly different, but very similar. The top bar buttons/links were moved to the right. Looks cleaner.
Ok, It is back to somewhat normal and they added a new feature to the site 
Oh nice! Marketplace in the browser!!
You must have caught them right as they were making the change.
They even have a rating system in place now