Thanks for your response.

I just come from the ackbarr site. He has a solution for my problem. He has modify the content of the following files : theme_blockleft.html and theme_blockright.html, to modify the way the block titles are displayed. He use a much more developped xoops_smarty syntax and call different css.

On the same time, I was searching for a solution more flexible. As the way the titles of the blocks are displayed, is manage by the theme + css. There is perhaps a solution in the xoops_smarty language. Instead of having one theme_blockleft.html, you create as much as you want : theme_blockleft_1.html, theme_blockleft_2.html,... inside your theme. Then, the problem is to call these files in theme.html. Is there a way to call these different files, by using the id of the blocks?
Can we do that with the xoops_smarty variables and syntax?

I need to have different look for my blocks. On a previous topic, I undestand that you can manage the look of your blocks through their templates.
But, in these template, you can manage the look of the content but not the look of the title of this block.
I suppose you have to work with the files of the theme : theme_blockleft.html...
But how to assign, for ex, a different look for the title of the main menu block and for the user menu block? These two blocks are left blocks...

Thanks for your response.