Msg#: 4081740 posted 1:15 am on Feb 17, 2010 (gmt 0)
Msg#: 4081740 posted 11:52 pm on Feb 20, 2010 (gmt 0)
You aren't going to alter the core content signifantly, just rearrange it and add some bells and whistles, a little window dressing so that in itself shouldn't have much of an effect on things ranking wise. Going from HTML to CSS usually means a good thing provided it is done cleanly. If you were to be going from HTML to server generated HTML there would most likely be some issues to resolve but all in all, in your case, I don't see a problem.
Msg#: 4081740 posted 8:08 pm on Feb 24, 2010 (gmt 0)
I would add that you want to be sure to keep all page names and URL paths the same.
With the drop down menu's, be sure that all the links are actual href links and NOT js links.
canadafred is right that usually there are no issues, especially if moving to a design that has a better text/code ratio, but any time you are doing a large change to the code that is output to the SE's, there is a risk it could have unexpected consequences.