I saw the code - Files 403.shtml, I think the index page is compromised. How can I save myself from this hack?

My website has been hacked lately and it has been defaced. Now I have weird files, and don't know where they are coming from. I just want to know, what of these files are harmful or can cause that I get hacked again.

The .htaccess contains the following code:

order allow,deny
allow from all

deny from 121.54.58.159
The file .wysiwygPro_preview_eacf331f0ffc35d4b482f1d15a887d3b.php contains the following code:
// display the HTML code:
echo stripslashes($_POST['wproPreviewHTML']);
?>