title: Errors/Warnings show up on "Error List" but then disappear for website project
body: <p><strong>BACKGROUND</strong></p>
  
  <p>I have inherited a solution with multiple projects. One of the projects is a website project... or at least I'm pretty sure that's what this icon means (It looks pretty different in VS 2010 vs 2013, so I'm showing both: VS 2013 on the left, VS 2010 on the right):</p>
  
  <p><a href="https://i.stack.imgur.com/G1gac.png" rel="noreferrer"><img src="https://i.stack.imgur.com/G1gac.png" alt="project icon"></a>  <a href="https://i.stack.imgur.com/3MdUi.png" rel="noreferrer"><img src="https://i.stack.imgur.com/3MdUi.png" alt="enter image description here"></a></p>
  
  <p><strong>PROBLEM</strong></p>
  
  <p>When I rebuild the website project, there are 8 warnings that are generated.  These correctly show up in the Error List, but only for a moment.  </p>
  
  <p><a href="https://i.stack.imgur.com/gS7Fh.png" rel="noreferrer"><img src="https://i.stack.imgur.com/gS7Fh.png" alt="Warnings show up for a second or two while build is running"></a></p>
  
  <p>Once the build process finishes, they disappear.</p>
  
  <p><a href="https://i.stack.imgur.com/SIrlG.png" rel="noreferrer"><img src="https://i.stack.imgur.com/SIrlG.png" alt="Warnings disappear as soon as build is complete"></a></p>
  
  <p>There are a few things to note:</p>
  
  <ol>
  <li>There are no filters set and I cannot toggle any of the message types because it says there are 0 of each.</li>
  <li><p>Even though the errors have disappeared from my Error List, they do still show up in the output section</p>
  
  <p><a href="https://i.stack.imgur.com/MPNY2.png" rel="noreferrer"><img src="https://i.stack.imgur.com/MPNY2.png" alt="Output window"></a></p></li>
  <li>Warnings and errors from other projects show up in the error list without any of this weirdness</li>
  <li><p>This is a website project, so the property pages are dramatically different than the ones that I'm familiar with.</p>
  
  <p><a href="https://i.stack.imgur.com/3bm5F.png" rel="noreferrer"><img src="https://i.stack.imgur.com/3bm5F.png" alt="property pages"></a></p></li>
  <li>I've observed the same behavior with errors</li>
  </ol>
  
  <p>I've tried different versions of VS and they both do the same thing. I've tried <a href="https://stackoverflow.com/a/6491440/1467396">deleting</a> my .suo file. I've played around with all the settings I can find that look at all relevant but nothing changes this behavior.</p>
  
  <p>What am I missing?</p>