Remove this site may be hacked google
and there are many more website like this search on google website malware scanner.
and please check on server and check any spam pages are generate on server.
Please delete and check .php files because hackers and spammers attack on website and leave backtrack so your website might hack again , I already remove many clients this error messages.
Remove the error message is easy while may be it hacked again so better talk with your developer and hosting provider company if you need my help please mail me at firstname.lastname@example.org