In the previous post the code example didn't get posted, so here is a new
try without the tag markers.
If you have this code
form id="form1" runat="server"
,and delete the / in /telerik:RadCodeBlock (unmatched tag), you get
telerik:RadCodeBlock id="form1" runat="server"
, as you see the form tag has been replaced with a telerik:RadCodeBlock tag.
This problem is there for every unmatched end tag.