Move to a theme that more closely matches what was there before.

experimental/webtry/res/css/webtry.css

 body {
   font-family: helvetica arial sans-serif;
   margin: 0;
   padding: 0;
 }
 
 img {
   box-shadow: 2px 2px 5px gray;
 }
 
@@ skipping 81 matching lines @@
 }
 
 #tryHistory .tries {
     float: none;
 }
 
 #gitInfo {
     float: right;
     font-size: 70%;
 }
+
+.CodeMirror-lines,
+.CodeMirror-scroll
+{
+  background-color: #eee;
+}
+
+.CodeMirror {
+  border: solid gray 1px;
+}