I suggest you start of by figuring out in which css class this line is defined. You can use Internet Explorer developer toolbar.
http://msdn.microsoft.com/en-us/library/ie/gg589507(v=vs.85).aspx
When I take a quick look I see it is defined in the class "s4-ca s4-ca-dlgNoRibbon and the id MSO_ContentTable. It is defined in the SMPortalCSS.css which is part of a of the SMPortalSharePointSiteFeatures, which you can find on the SharePoint server in
the 14 hive:
c:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\FEATURES\SMPortalSharePointSiteFeatures\CSSModule
After that it is your basic SharePoint branding, you should check Heather Solomon her blog. She has written a lot of blogs about SharePoint branding\styling.
http://sharepointexperience.com/csschart/csschart.html
You can create for instance your own theme next to the basic SMPortal which also uses the SSP specific css classes.
Hope this helps!