Dialog box Styling in SharePoint 2010

SharePoint 2010 has two important classes to control the dialog display
.s4-notdlg
.ms-dialog


s4-notdlg
Apply the class to any div which is not required to disply

ms-dialog
This class is added to the tag of dialog, so we can modify the css of any class in the dialog.
e.g.
.ms-dialog .ms-cui-topBar2
{
   height:0px;
}