Buying Games on Steam

I was very disappointed in steam because they don't really seem to fix their issues.When i want do but a game it says: "An unexpected error has occurred. Your purchase has not been completed." or "Your purchase has not been completed. Your credit card information has been declined by your credit card company.

Note that in some cases, your credit card company may put a 'hold' on funds in your account, but you will not be charged. After reviewing the information below, if you believe your card has been declined in error please try your purchase again.".There are many other people having this problem and i really can't find any solution.I've been using the credit card to buy other things on other websites and it works!

I am really pissed off. How can such a professional site has such issues?!