Improve use of CSS font-weight

bibtexbrowser.css

@@ -11,14 +11,14 @@ body {
 }
 .sheader {
     font-size: 1.5rem;
-    font-weight: 600;
+    font-weight: 700;
     padding-top: 1.5em;
     padding-bottom: .5em;
 }
 .theader {
     display: block;
     font-size: 1.25rem;
-    font-weight: 600;
+    font-weight: 700;
     padding-top: .5em;
     padding-bottom: .5em;
 }
@@ -29,6 +29,9 @@ td.bibitem {
     padding-left: 1.5rem;
     display: block;
 }
+.bibtitle {
+    font-weight: 700;
+}
 a {
     color: #C01632;
     text-decoration: underline;