ok, here's a typical situation, i hope its relevant for you
i would guess that index.php for example, which is in the root folder, has a path to the css which looks like...
<link rel="stylesheet" media="all" type="text/css" href="css/content.css" />
or something like that.
files within your admin folder, with the above path will not point to the css file
you would need something like
<link rel="stylesheet" media="all" type="text/css" href="../css/content.css" /> (note the ../ which takes you back a folder)
if this doesn't help, post a page which works and one which doesn't, and i will try to help further.
if, when you created the admin pages, they were based on a template, this should have been done for you automatically in dreamweaver.
also, when the page is open in dreamweaver, all of the linked pages should be shown under the page tab.
if you try to click on one of these and it isn't where it should be, an error messge will be displayed.