diff --git a/resources/function_help/json/concat b/resources/function_help/json/concat
index 5c705db6bd6..d4b524ca696 100644
--- a/resources/function_help/json/concat
+++ b/resources/function_help/json/concat
@@ -1,9 +1,10 @@
 {
   "function": "concat",
-  "description": "Concatenates several strings to one.",
+  "description": "Concatenates several strings to one. NULL values are converted to empty strings.",
   "variableLenArguments": true,
   "arguments": [ {"arg":"string1", "syntaxOnly": true},
                  {"arg":"string2", "syntaxOnly": true},
                  {"arg":"string", "descOnly": true, "description":"a string value"}],
-  "examples": [ { "expression":"concat('a','b','c','d','e')", "returns":"'abcde'"}]
+  "examples": [ { "expression":"concat('a','b','c','d','e')", "returns":"'abcde'"},
+                { "expression":"concat('The Wall', NULL)", "returns":"'The Wall'"}]
 }
diff --git a/resources/function_help/text/AND b/resources/function_help/text/AND
index ac88fe40d5b..e4aaa40a9be 100644
--- a/resources/function_help/text/AND
+++ b/resources/function_help/text/AND
@@ -7,7 +7,9 @@ Returns 1 when condition a and b are true.
 <h4>Arguments</h4>
 None
 
-<h4>Example</h4>
-<pre> 4 = 2+2 AND 1 = 1  &rarr; returns 1 </pre>
-<pre> 4 = 2+2 AND 1 = 2  &rarr; returns 0 </pre>
+<h4>Examples</h4>
+<pre> TRUE AND TRUE  &rarr; 1 </pre>
+<pre> TRUE AND FALSE  &rarr; 0 </pre>
+<pre> 4 = 2+2 AND 1 = 1  &rarr; 1 </pre>
+<pre> 4 = 2+2 AND 1 = 2  &rarr; 0 </pre>
 
diff --git a/resources/function_help/text/|| b/resources/function_help/text/||
new file mode 100644
index 00000000000..2f13c6d05ff
--- /dev/null
+++ b/resources/function_help/text/||
@@ -0,0 +1,14 @@
+<h3>|| concatenation operator</h3>
+<p>Joins two values together into a string.</p>
+<p>If one of the values is NULL the result will be NULL. See the CONCAT function for a different behavior.</p>
+
+<h4>Syntax</h4>
+<pre> value1 || value2</pre>
+
+<h4>Arguments</h4>
+None
+
+<h4>Examples</h4>
+<pre> 'Here ' || 'and ' || 'there' &rarr; 'Here and there' </pre>
+<pre> 'Nothing' || NULL &rarr; NULL </pre>
+<pre> 1 || 2 &rarr; '12' </pre>
diff --git a/src/gui/qgsexpressionbuilderwidget.cpp b/src/gui/qgsexpressionbuilderwidget.cpp
index dd324fadedb..1f3d5a8689c 100644
--- a/src/gui/qgsexpressionbuilderwidget.cpp
+++ b/src/gui/qgsexpressionbuilderwidget.cpp
@@ -362,6 +362,7 @@ void QgsExpressionBuilderWidget::registerItem( QString group,
     newgroupNode->setData( group, Qt::UserRole );
     newgroupNode->setData( group == "Recent (Selection)" ? 2 : 1, QgsExpressionItem::CustomSortRole );
     newgroupNode->appendRow( item );
+    newgroupNode->setBackground( QBrush( QColor( "#eee" ) ) );
     mModel->appendRow( newgroupNode );
     mExpressionGroups.insert( group, newgroupNode );
   }
@@ -439,12 +440,7 @@ void QgsExpressionBuilderWidget::updateFunctionTree()
   registerItem( "Operators", "<>", " <> ", tr( "Unequal operator" ) );
   registerItem( "Operators", "<=", " <= ", tr( "Less or equal operator" ) );
   registerItem( "Operators", ">=", " >= ", tr( "Greater or equal operator" ) );
-  registerItem( "Operators", "||", " || ",
-                QString( "<b>|| %1</b><br><i>%2</i><br><i>%3:</i>%4" )
-                .arg( tr( "(String Concatenation)" ) )
-                .arg( tr( "Joins two values together into a string" ) )
-                .arg( tr( "Usage" ) )
-                .arg( tr( "'Dia' || Diameter" ) ) );
+  registerItem( "Operators", "||", " || " );
   registerItem( "Operators", "IN", " IN " );
   registerItem( "Operators", "LIKE", " LIKE " );
   registerItem( "Operators", "ILIKE", " ILIKE " );