AbleCommerce Shopping Cart Software

I need to create several landing pages.

I have created a webpage.aspx file for each and left and right side bars for each.

However wehn I change the sidebar on one it changes it for all of them.

Am I missing something?

You're not really missing anything, you're falling into the pit a lot of us fell in when we started.
Whenever you change any of the 6 fields in the Editor Zone at the bottom of a webpage, you change it for all the pages that use that same display page. If you create new webpage(x).aspx files, you have to create a new Web Page(x).htm in the App_Data/Scriplets/Custom/Content folder and set the .aspx page to use the appropriate one.