Prevent Malware and Hacked

Using the below we can say that Site hacked or not..
http://www.google.com/safebrowsing/diagnostic?site=www.yahoo.com

I Heard normal hacking is
1.XSS(cross scripting)
2.SQL injection

One of my client site has been infected by same scenario
(some JS has been inserted into homw page ,eventhoug i delete it will update with in 2 hrs)
http://www.google.com/support/forum/p/Webmasters/thread?tid=5f46270bc7fd5b4a&hl=en

I have answerd for that issue..

suggestion

1.when you are using the FTP or content management tool to upload the code ,make sure that pc dont have malware or virus (otherwise hacker will st the UID and PWD)..

2.Go for well protected webhosting service...