diff --git a/layout/html/document/src/html.css b/layout/html/document/src/html.css
index d9b4381f5608..41fe2b0b9cfc 100644
--- a/layout/html/document/src/html.css
+++ b/layout/html/document/src/html.css
@@ -971,6 +971,8 @@ select[size] {
 }
 
 select, select[size="1"] {
+  font-family: sans-serif;
+  font-size: small;
   background-color: white;
   border: inset 2px rgb(192, 192, 192);
   padding-left:   0px;
@@ -1196,6 +1198,8 @@ option.selectedfocus {
 }
 
 optgroup {
+  font-family: sans-serif;
+  font-size: small;
   display:block;
   font-style:italic;
   font-weight:bold;
diff --git a/layout/style/html.css b/layout/style/html.css
index d9b4381f5608..41fe2b0b9cfc 100644
--- a/layout/style/html.css
+++ b/layout/style/html.css
@@ -971,6 +971,8 @@ select[size] {
 }
 
 select, select[size="1"] {
+  font-family: sans-serif;
+  font-size: small;
   background-color: white;
   border: inset 2px rgb(192, 192, 192);
   padding-left:   0px;
@@ -1196,6 +1198,8 @@ option.selectedfocus {
 }
 
 optgroup {
+  font-family: sans-serif;
+  font-size: small;
   display:block;
   font-style:italic;
   font-weight:bold;