In your MasterPage, you will add ContentPlaceHolder controls; those controls will be a marker where content from the content page should be located.
Create your MasterPage as how it should look like, add the ContentPlaceHolders into the MasterPage where you want to have your content from the Content Page (Content page is the page that uses the MasterPage). The Content Page use the Content control to specify the content that should be displayed within a ContentPlaceHolder located in the MasterPage.
So make sure your HTML in the MasterPage is correct written to support your layout, and also that you add the correct content to the correct content control within your content page.
/Fredrik Norm?n NSQUARED2
Microsoft MVP, MCSD, MCAD, MCT
CornerstoneMy Blog, ASP.Net 2.0 etc