diff --git a/suite/common/pref/pref-charset.xul b/suite/common/pref/pref-charset.xul
index e52b43b4ff40..e4fffcca8f46 100644
--- a/suite/common/pref/pref-charset.xul
+++ b/suite/common/pref/pref-charset.xul
@@ -49,7 +49,10 @@
       <!-- Available Charsets Tree -->
       <tree class="inset" id="available_charsets" flex="1" onselect="SelectAvailableCharset();" 
             datasources="rdf:null" indent="false" multiple="true">
-        <treechildren id="available_charsets_root"/>
+        <treecolgroup>
+          <treecol flex="1"/>
+        </treecolgroup>
+        <treechildren id="available_charsets_root" flex="1"/>
       </tree> 
       <separator class="thin"/>
       <box autostretch="never">
@@ -62,7 +65,10 @@
 	    <text class="label" value="&charset.customize.current.label;" crop="right"/>
       <tree class="inset" id="active_charsets" flex="1" onselect="SelectActiveCharset();" datasources="rdf:null"
 	          indent="false" multiple="true">
-        <treechildren id="active_charsets_root"/>
+        <treecolgroup>
+          <treecol flex="1"/>
+        </treecolgroup>
+        <treechildren id="active_charsets_root" flex="1"/>
       </tree>
       <separator class="thin"/>
       <box autostretch="never">
diff --git a/suite/common/pref/pref-languages-add.xul b/suite/common/pref/pref-languages-add.xul
index 9662fb0fcad3..79d4799f52ab 100644
--- a/suite/common/pref/pref-languages-add.xul
+++ b/suite/common/pref/pref-languages-add.xul
@@ -44,7 +44,10 @@
 
   <tree class="inset" id="available_languages" flex="1"
         datasources="rdf:null" multiple="true">
-    <treechildren id="available_languages_root"/>
+    <treecolgroup>
+      <treecol flex="1"/>
+    </treecolgroup>
+    <treechildren id="available_languages_root" flex="1"/>
   </tree>
 
   <box autostretch="never">
diff --git a/suite/common/pref/pref-languages.xul b/suite/common/pref/pref-languages.xul
index 613474306c56..53c93fa321bd 100644
--- a/suite/common/pref/pref-languages.xul
+++ b/suite/common/pref/pref-languages.xul
@@ -41,15 +41,17 @@
     <box>
       <box orient="vertical" flex="1">
         <tree id="langTree" class="inset" flex="1">
-          <treecol style="width: 10%"/>
-          <treecol />
+          <treecolgroup>
+            <treecol flex="10" width="0"/>
+            <treecol flex="90" width="0"/>
+          </treecolgroup>
           <treehead>
             <treerow>
               <treecell />
               <treecell value="&languageColumnHeader.label;" />
             </treerow>
           </treehead>
-          <treechildren>
+          <treechildren flex="1">
             <treeitem>
               <treerow>
                 <treecell class="propertylist" value="&engOrder.label;"/>