Again Steam is doing another promotion, this time on Counter-Strike Source. The only difference is that now they are cutting off 75% on the price of CSS, makig it 5$ or something like 3.75 Eur, which is surely good news for those who share accounts or just want to have a backup account (for cheaters too, but for those they should charge extra instead of cutting off the price).

You can see all of the details at Steam's Store and keep in mind that this is only for the weekend. Retail price is usually 19.99$, somewhere in the vicinity of 15.00 Eur.