Hi there. I added Twitter Card meta tags to one of my pages, and used the validator, found here, to test it:
It worked. The meta tags were in the BODY tag (long story, but I had to work around a templating system issue), but the validator read them all (it listed the number it found) and the preview was correct. Then, when I tweeted it out, it didn’t pick them up. It worked fine after I moved them to the header. No issue with the meta tags having to be where, semantically, they should be, but the validator, I assume, shouldn’t say they’re fine elsewhere if they’re not.