Never trust a smiling Garfield!
It appears that you are not loading the CSS specifications, but there isn't enough information to troubleshoot.
Operating system/browser & version?
Edit - You said that you have had the problem "for a while." The masses would scream if everyone was seeing this.
Yeah, I've seen this before (not very often tho, maybe a couple times a year?) but a reload solves it, this time around it was about half an hour before it resetted back to it's normal state.
Once it did that the site loaded normally but the images in the galleries were all broken which again resolved itself after 10 to 15 minutes...
It kinda looked like the image server, which also hosts the css and js, was not available.
What can happen tho that the load balancer put me onto a server that had issues for a bit that wasn't being used by 'the masses' so only people who were put on that one got the issues.