SQL Injection removal

You might find that you have had the text fields in your database appended with the following text "<script src=....."
We had that happen. Here's part of what's wrong. Say you're running an e-commerce site, right? And when you go to a product page, you'll do something like a URL that says http://www.whatever.com/product.asp?ProdID=5
And that's fine...unless you allow dbo (Database owner) rights to your DB through the user name.
I had this happen to a client recently (I didn't make the site myself). Here's what I did to correct the problem:
1) I wrote an ASP script that sanatized my db
2) I made two SQL login accounts. One that had DBReader rights, and the other was DBWriter. The one with DBR is for showing stuff, and DBW is for putting stuff in.
3) Sanatize your Request variables before using them! For instance, if your product id is numeric field, the check to see if the Request.QueryString in the above example can be parsed as a number! If not, then drop it. Strip odd characters (such as quote, double quote, and semi-colons) from your data before mating it to a SQL statement. Better yet, use a parameterized query or stored procedure to recall your data from the DB.

CCongdon is exactly correct. The problem comes in when a user tries to add SQL commands to the fields in your pages like

;select * from syslogins;

if your fields are not checked and the user has permissions then the user could get all the information requested or execute commands as desired. This is a very simplified example.