iPod touch 3rd-gen won't play videos in Safari
THat circle with a line cross through it means that the format is not supported on the iPod Touch, or any other iOS device. 

It is usually related to flash video's.
If you are looking at a youtube video go check out m.youtube.com. It should load most videos to play just fine.

However if the source of your video is not a youtube (or other big site) then you may be out of luck.