Type ‘System.Web.UI.ScriptManager’ does not have a public property named ‘MultiView’ I am using WebExpressions 3. What does this mean?

Also, if you go to my website www.emeraldcitylandscapecompany.com you will notices that on several pages the header or top of the page is all messed up with text rolling over to another line, it gets reduced in size on one page and has a box around it on another. How does that happen since it is in my Master.DWT and should be the same across all pages.

Thanks for your help.