The usual behavior of a random viewer, when presented with a new, auto-resized browser window after they click a link, is to close it before it's done loading. but that's only if their browser add-ons allow it to pop-up in the first place (most anti-pop-up add-ons won't allow it anyway). Generally, they're a bad idea and there's usually a better way, like using a modal window.
What Ben is saying is your code is malformed. Change...
<p><a href="#" onclick="MM_openBrWindow('2012.html','2012Underwriters','width=600,height=675')">- 2012 - </a> <a onclick="MM_openBrWindow('2013.html','2013Underwriters','width=600,height=675')">- 2013 - </a></p>
to...
<p><a href="#" onclick="MM_openBrWindow('2012.html','2012Underwriters','width=600,height=675')">- 2012 - </a></p>
<p><a href="#" onclick="MM_openBrWindow('2013.html','2013Underwriters','width=600,height=675')">- 2013 - </a></p>