I’m thinking of advertising my site (web designing) in google via adwords.
I don’t know adwords system at all so I’d like to ask you if this is this good idea?
I mean is it worth to spend money on it?

Google Adwords is OK. It can quickly bring traffic to your site; and you can conveniently know the conversion rate.

Yeah I agree with Hyena. This is something you have to test, optimise then test some more.

It all depends on what you sell, your market, your price point, your conversion rates, etc.

What are you trying to sell?

This is a bit like asking it is worth advertising your site on tv?

Dunno, you tell us? What are you selling? Can you afford it? Surely you’d try it rather than just let a forum thread decide for you?

Yes, it worths, but pay attention to the conditions, where will appear your url, in what kind of pages, if there are related, niched websites, because you need to reach to a target.