ALT tag limitation

Greetings W3C team,



I am working on accessibility and I would like to solve a minor question
about WCAG 2.0. I am doing a deep investigation on screen readers and I have
contacted my peer in Freedom Scientific for JAWS questions and he told me
W3C recommends ALT text shorten than 255 chars. However, my peer does not
have the exact location of the information in the WC3's site. I also have
done a search in WCAG pages and didn't find anything about this limitation.



I know alt tag should be as brief as possible, but I would like to know how
many chars would be considered as a violation for WCAG 2.0. Would you mind
to help me on this?



Thanks in advanced,



Best regards,

Rodrigo.