I have a site where I want to run an older (3.7.7) and current Ata themes. The older one will be used for a placeholder site that will be up until the site is ready to go live (3.7.10).

I've done this before but it was a much older version (3.5.3). For some reason, the CSS is pulling the same settings for each. (i.e. Changing CSS or a setting on one updates the other.) Is there a way to distinguish the two? Or do I have to find a copy of 3.5.3 to install?

If you mean you have two sites sharing the same database and it's not a multi-site, that is a very bad idea for many reasons. A very bad idea.

No, let me try to clarify. I'm not trying to run a multisite. I want to have a placeholder (bare bones) version of the site while I do back-end work on the full version of the site. Once the full version goes live, the placeholder disappears into the ether.

I'd like to do the placeholder on an older version of Ata just because I can get it done faster. Then switch to the current version during off hours to work on the full version of the site, and revert back to the placeholder during business hours.

If necessary, I can just use the 2012 theme or something like that. It's really that basic. The details are just easier with Ata.

The setting for Atahualpa are all stored in the database so you cannot install two different version and change each individually. As you found when you make a change it affects both.

The only way I can think of doing what you want is to build another site as your dev site and work through the transfer when done.

I'm not sure what you mean by using Twenty Twelve or why working on the older version of Atahualpa is easier.

if it is litterally a place holder, here is what I would do. Set the home page like you want it then in the browser, use the view source to see the sourc e of the page. Copy it, put it in a file and call it 'index.html'

Next upload it to the wordpress root folder and then you should see it when you use mydomain.com.
To get to the site, yse mydomain.com/index.php