Hi Eric,
From what I can see, the page you are trying to edit is not using the "Snippet Tag" feature of Snippetmaster to specifically make only certain portions of the page editable.
So.. when you edited the page, you probably used the "Whole File" editing method. (The entire file was loaded into the editor, instead of just the portion of the page you actually need to edit.)
As a result, the web page seems to have been messed up by the editor, because there was some incomptable code inside...
To answer your questions:
1. No, at the moment SnippetMaster does not take any backups before modifying a file. This is a feature I'm adding for the next version. For now, you'll need to contact your web hosting provider and ask them to restore this file from a backup.
2. You should use the Snippet Tag feature (
http://www.snippetmaster.com/documentation/snippet-tags.html) to specify certain portions of your page as editable. This way, when you load the file in snippetmaster, ONLY the portion of the page you want to actually edit will be modified.. instead of the entire page, which in your case is a problem due to something in the page itself that conflicts with the editor. (Could be an incorrectly coded HTML page or something..)
I hope this helps... once you get the file restored, let me know if you need a hand with setting up the Snippet Tag feature, and I'll do my best to assist.