First you need to sort out why your site is loading the skin.css six times. Have you included links to the skin.css in a bunch of different places? Remove all references to it and let DNN load it just once from the skin folder.
Also, one of the skin.css files is completely different from the others. The one loading five times says 2007 at the top and the other says 2006.
Also, (and I put this in a ticket in Gemini long ago) made-up classes are case sensitive in some browsers. DNN tends to use Normal instead of normal. You should use exactly the same capitalization as is in the code.
There's also a Normal style specified in your portal.css
All up and including the default.css, the module is looking at 8 places where the normal styles has been specified.
Oh.. hang on.. there's more! You've even got the normal style specified more than once in the skin.css
Remove them all, then copy the .Normal section out of the default.css into your skin.css and set the desired size.
The best way to style is to start with nothing and then only add what is needed. Also always be aware that the defaul.css is pre-styling everything and you have to override exactly what it is doing.
And dont' go a step further until you've insalled Firefox and the Web Developer and Firebug Add-ons. These are essential and you can't carry on until you have them. Use the Edit CSS menu in Web Developer and the Inspect Element right-click item in Firebug.
Rob