Unfortunately, as far as I know, a plain old <select> control cannot have form controls in its options. I think you will need to use JavaScript. On that page, clicking the "button" (it's simulated, actually) displays an unordered list. List items have the flexibility to include checkboxes.

It's not about form controls in the <select> it's about what the <select size="1" multiple> looks like. <Select> *is* a form control.

The problem is that when I want a compact control with multiple selection the standard alternative looks bad and is difficult to understand for the user.

The address I mentionned shows the way <select size="1" multiple> should look and work.

I guess the Mozilla development community is the community that can make it so.

Thank you

You can file a request for enhancement in the bug tracking system: https://bugzilla.mozilla.org/. But if you know anyone enthusiastic about writing the code, that probably is even more important.

Thank you for your suggestion. I did a post on bugzilla.

Thanks