Ok, thanks for you two replies :D
I'm search the documentation during all the day and I'm about to think that's it's impossible :( But that's not a very important problem for me.
Thanks Swen for your 2 links, I'll investigate this soon ... But the solution seems to be a little "heavy" and seems to broke the W3C standard ... But I'll try it ... just to see :D
Many thanks,
Best Regards.