When your site is defaced, it means it's completely compromised, it doesn't work as supposed and the attacker is telling everyone visiting it that it was hacked. There might be often other types of malware included such as backdoors, hacktools or spam content.
This malicious code affects any vulnerable or compromised website that is configured to interpret the script language.
Inspect your site's files, specially theme related, to find for code you don't recognize. Look for any encoded or obfuscated PHP code.
Also, you can sign up with us and let our team remove the malware for you.
<meta http-equiv="Content-Language" content="en-us">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>HaCkEd By Prosox </title>
<meta name="keywords" content="HaCkEd By Prosox">
<meta name="description" content="HaCkEd By Prosox">
<center><font face="LilyUPC" size="8" color="#0066FF">Hacked </font><font face="LilyUPC" size="8" color="#FFFFFF">By Prosox
<img alt="http://i.skyrock.net/8707/85138707/pics/3216954359_1_8_qG35Sy6J.gif" src="http://i.skyrock.net/8707/85138707/pics/3216954359_1_8_qG35Sy6J.gif">