Doesn't this issue relate to some specific comment system (as Disqus)? It could be the server side what's broken. You were obviously able to post your question here, so the POST requests from your browser make theyr way out to the internet.

Yes I was able to post here but... only here !...

I tried several blog on which the same bug appears... I had to go on chrome to post my comment !....

But you still didn't share the url of the blog so that we can find out? One would think you are doing your best to avoid getting any help.

Sorry I did not read well...

Here are two link on which I tried to post :

1) http://www.2012un-nouveau-paradigme.com/2014/05/a-vancouver-le-cannabis-s-achete-au-distributeur.html

2) http://www.agenceinfolibre.fr/francois-danglehant-repond-au-pseudo-maitre-eolas/

Thanks for your help.

I had no problems posting on these sites. I suggest to try the following:

• Try a different browser to check if this is a browser related problem
• If it works in another browser, try to disable addons in your browser
• if it does not work in other browser your IP address might be banned. Try using proxy, such as Tor Browser (based on firefox by the way)

I tried with Chrome and it worked...

I tried FF with all addons dissble it doesn't work....

I am not banned from those website, I am sure of it...

This is really strange. I can only recomend the casual stuff:

• Check for updates on firefox
• Delete cookies for that page
• Look for errors in the console (Ctrl+Shift+J)

I think the error is on the site, not in Firefox.