Can't place a breakpoint in asp.net master page file

I have an MVC web application. I get an "Object reference not set to an instance of an object" error in line 16 below. It's a master page file. When I try to place a breakpoint in that line or anywhere in the file, I get a "this is not a valid location for a breakpoint" error. I have clicked on every line and I can't place a single breakpoint. I do have lines which have code only.

How do I place a breakpoint in this file?

Note: I can place breakpoints in code files. In some other aspx files, I can place a breakpoint in some code lines and some not. Does the inline code have to be in a special format to place a breakpoint? Using VS 2010 in Windows 7 64bit.

Code:

Line 14: 开发者_开发问答  <div id="<%= Model.PageWidth %>" class="<%= Model.PageTemplate %>">
Line 15:     <div id="hd">
Line 16:       <h1><a href="/"><%= Model.Workspace.Title %></a></h1>
Line 17:       <h2><%= Model.Workspace.Subtitle %></h2>
Line 18:     </div>

Look at this post: Break points aspx pages

If you are developing locally the "Script Documents" will show up under "Windows Internet Explorer" and you can add the breakpoint on the dynamically generated file there.