What you're seeing is the alt text for what should be little icons, which for some reason didn't download / aren't showing.

But why does it happen sometimes.

Ask your browser?

Wish it were that intelligent to answer that kind of question.....
Anyways will have to find a quick hack on my own.

Sometimes, I get huge font words, mixed with normal sized words when browsing forums, but soon as I hit "refresh" button all gets back to normal. I think it is a communication glitch between me and ISP. No big deal.

Edit: quite often I see little icon in my status bar saying "done, but with errors."

The Done but with errors is sometimes due to the advertisements - I've seen that myself.

Yes, those are javascript errors. Double click on that icon and a window will pop up showing what errors are on that page regardign javascript syntax and all that. If you know Javascript , you would be able to understand most of what it is saying.

Those huge font... they were advertisements.

I'm not sure what huge font words you're talking about.