Comment tags 

you have NO message...but thank a lot...i never know if it's better to thank people(loose their precious time+ incrase trafic on Special:Recentchanges) by the way is there any "very advanced" mediawiki howto for doing things such as 
< !  >
No problem, and I think many people appreciate a user saying "job well done."  The commenting feature of HTML (the bracket exclamation point business) makes text invisible.  For instance, if you were to look at "edit this page" you could see a sentence here: .   This is occasionally done in articles for a variety of reasons:
Put in a notice about vandalism (such as is done on Chuck Norris, which is also, at present, semi-protected), or when the same mistake is made by many users,
Automated bots sometimes also "remove" an image by enclosing it in comments, when the image may be added incorrectly.
In rare cases, text additions are put in comments so that other editors can see them, before the material is added to the article properly.  This is usually a bad use of the comments, since it makes things confusing to edit.
They often appear at the end of semi-automated template messages, to indicate which message was used (that is where the "Template:Unsigned").  So, for instance, I wrote {{subst:unsigned|00 tux}}, and the unsigned template was added.  If you want to try out some templates (which are always enclosed in two curly-braces) in the Wikipedia:Sandbox, a pretty good list of common template messages is available at WP:TM.
Thanks,