My Site has disappeard-HELP

My host company says that all is well at their end. but when I attempt to go to my site I get blank sheets. IE gives me an error message that says website cannot display the page:Most likely causes:
•The website is under maintenance.
•The website has a programming error.
The only files I changed were the Header.php file.

the header.php file in the admin/includes directory is 129944 bytes.
the header.php file in the includes/language/english directory and in a couple of other locations is 2433bytes.

Could this be causing my site to totally disappear? If so should I resort to returning all the headers.php to their original status which is the 129944bytes.
Any help again would be appreciated:cry:

admin/includes/header.php should be about one-tenth that size.

I would replace any files you changed with fresh files fron a new copy of the Zencart files and start over.

Thanks, I was afraid of that:frusty: