As-Salamu alaykum Hassan ..
As Plutarck stated .. you'll need to have a Merchant Account to be able to charge your customers' visa cards ..
The Merchant account is provided with many companies in the Internet .. you can go to google.com and type : merchant credit card account ..
But note that they charge you for providing you with this service .. and it depends on : Where are you living .. How much money will you make from the site ..
Usually fair offers consume 2.5% of your income .. and they charge you monthly for something like 30$ .. as I said there is no solid prices here .. every company has a seperate offer.
I hope that I've answered your question ..
Salaams,
Wael