Add to cart button doesn't add - from any page

No...Dr Byte -- IS AWESOME!!!!
That was the problem. I can't thank you enough.
One last thing -- for now -- to backup the site I have run the backup through cpanel and stored the .tar file on my computer, but I also want to transfer my /public_html/ file from my server back to my computer through the FTP and place it in a "backup" file. My rationale is that if anything goes wrong I can just re-upload those file through the FTP and be back at this point. Is that correct?
Thanks again!!!

I have noticed one more issue that I think is probably related to the previous fix. My /store/admin isn't functioning. When I edit anything, it just takes me back to the admin home page and doesn't record the change.

This how the /store/admin/includes.php file reads:
define('HTTP_SERVER', 'http://mark-a-hydrant.com');
define('HTTPS_SERVER', 'https://secure66.inmotionhosting.com/~markah5');
define('HTTP_CATALOG_SERVER', 'http://mark-a-hydrant.com');
define('HTTPS_CATALOG_SERVER', 'https://secure66.inmotionhosting.com/~markah5');
should this also be changed to "http://www.mark-a-hydrant.com" ?
Thanks.

I made the change and it took care of it.
Thanks.