a way to test broken themes

Okay, I had this problem with disappearing themes and disappearing content. Very annoying. After changing the theme inside the admin panel, the site would work for a little while and then just go away – no error or 404, the page would just become completely blank.

After playing with it for awhile, I discovered that some themes work just fine, no problem, while other themes seemed to create problems. So I’ve come to the conclusion that somehow those themes are broken.

But here’s the thing. I have some knowledge of HTML, enough to sometimes make small changes to a theme, but I am far from proficient in it.

So here’s my question: Is there a website or program out there, that I can use to test my themes, which will tell me what section of code is broken?