Hello Olafur
You create the style in your skin.css file.
Within your skin and in between HTML < > tabs you will need to manually insert your , runat server, also the name you have chosen to call the content pane or that section of your skin and the class you have created associated with that pane.
runat ="server" id ="LeftContentPane" class="myleftpaneStyle"
If you are using Dreamweaver, you can use Dreamweaver extension for DotNetNuke skinning, found here:http://www.thinkofdesign.com/Produc...fault.aspx
You will find that all you need to do is select insert in your tool bar for a dropdown menu of DNN skinning properties which upon selection can then be inserted into your skin as required.
I know it sounds complicated but I suggest you download and view sample skins just to see how they look and how they have been created. It is not as difficult as it seems.
You will find sample skins to download at the above link and also Lee has some sample skins on this site. I suggest also that you view the skining tutorials on dnncreative I think that some skins accompany the tutorials, for you to study.
Good luck
Lynn