Should not lock the icon in the addon bar... Rated 4 out of 5 stars

I'm giving this a 4 star rating merely for the fact the the icon/button is locked in the addon bar. This leaves users that want to keep the addon bar hidden with no alternative.

I'm willing to change my rating to 5 stars if the maintainer would make it so that the icon can be placed in any toolbar ;)

Really cool. But should support longdesc attribute too. Rated 4 out of 5 stars

Semantic Checker is really cool. (Although, like Xavier, I did not see the addon until I read your comment to him about the addon bar.)

But one thing:Could you add @longdesc to the list of semantic features that this checker supports?

For the record, the HTML5 validator now accepts @longdesc on the img element. And there is even a spec for it - see
https://dvcs.w3.org/hg/html-proposals/raw-file/default/longdesc1/longdesc.html

nothing Rated 5 out of 5 stars

je ne vois rien dans mon navigateur qui correspondent à cette extention.
I do not see anything witthat plugin
[Edit] Merci thanks Nico

works for me

Just tested with a Firefox 15 - for me it works like expected. After installing the addon you should see a small yellow icon in the addon bar at the bottom right corner of your browser (the addon bar is not there by default, you have to activate it). Click it and page elements were highlighted.