Be careful which site you choose, Mona.
Last year, I got a couple of magnets from a site called AllPosters.com. They have a huge number of related sites, so I thought it seemed safe enough.
But their system was hacked and my bank details taken. What really hacked me off was that instead of sending me an email telling me so, so I could deal with it immediately, they sent me a snail mail letter from New York, which took two weeks to reach me!
Fortunately, my bank was on the ball, noticed the item for iTunes which the hackers used to test the account and alerted me. I had to be issued with a new debit card, but otherwise dodged the bullet.
So just tread carefully.
LabRat