A temporary work around for the fact that the To and cc fields haven't been wrapping. This is actually a xul bug

where xul elements inside of an html div weren't being displayed as inline by default. My temp workaround is to
explicitly declare each element in the html tag with a display: inline style. Thanks to evaughan for giving me this idea.

themes/modern/messenger/msgHdrViewOverlay.css

@@ -29,6 +29,7 @@ Rights Reserved.
 
 mail-emailaddress {
   behavior: url(chrome://messenger/skin/mailWidgets.xml#mail-emailaddress);
+  display: inline;
 }
 
 spring.buttonTopSpacer     { height: .3em; }
@@ -55,6 +56,10 @@ image.emailDisplayImage
   align: right;
 }
 
+text.emailSeparator {
+  display: inline;
+}
+
 text.emailDisplayButton {
   color: blue;
   text-decoration: underline;
@@ -64,10 +69,12 @@ text.emailDisplayButton {
 
 button.showMoreAddressesButton {
   list-style-image:url("chrome://messenger/skin/more.gif");
+  display: inline;
 }
 
 button.showFewerAddressesButton {
   list-style-image:url("chrome://messenger/skin/less.gif");
+  display: inline;
 }
 
 html.headerValue   { white-space: normal; min-width: 50px; }