diff --git a/doc/common/doxygen.css b/doc/common/doxygen.css
index 48563b473..932e6975a 100644
--- a/doc/common/doxygen.css
+++ b/doc/common/doxygen.css
@@ -94,3 +94,16 @@ SPAN.comment       { color: #800000 }
 SPAN.preprocessor  { color: #806020 }
 SPAN.stringliteral { color: #002080 }
 SPAN.charliteral   { color: #008080 }
+
+.line {
+text-align: left;
+font-family: monospace;
+}
+
+.lineno {
+display: inline-block;
+width: 3em;
+margin-right: 5px;
+background: #EEEEEE;
+text-align: right;
+}