I've done this "Professional Webdesigner" course once. Even though I learnt quite a lot, I don't think they're worth much compared to, for example, college. And it wouldn't have been enough to get any "real" job, I learnt most of the things I know myself, still. I don't think putting a course on your CV would get you the job if there's competition. But if you have some spare time to kill, it can't hurt either. It's a nice little extra.
Try looking for one where you actually get certified. The course I did led to two certifications from an independent party (CIW).
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Common sense is the collection of prejudices acquired by age eighteen.