diff --git a/content/html/style/src/nsCSSDeclaration.cpp b/content/html/style/src/nsCSSDeclaration.cpp
index 202be1bd68c0..c08f2aa47460 100644
--- a/content/html/style/src/nsCSSDeclaration.cpp
+++ b/content/html/style/src/nsCSSDeclaration.cpp
@@ -1610,7 +1610,9 @@ CSSDeclarationImpl::AppendValue(nsCSSProperty aProperty, const nsCSSValue& aValu
             break;
           case eCSSProperty_user_focus:       mUserInterface->mUserFocus = aValue;      break;
           case eCSSProperty_resizer:          mUserInterface->mResizer = aValue;        break;
-          case eCSSProperty_behavior:         mUserInterface->mBehavior = aValue;       break;
+          case eCSSProperty_behavior:         
+            mUserInterface->mBehavior = aValue;      
+            break;
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
       }
@@ -3046,7 +3048,9 @@ CSSDeclarationImpl::GetValue(nsCSSProperty aProperty, nsCSSValue& aValue)
             break;
           case eCSSProperty_user_focus:       aValue = mUserInterface->mUserFocus;       break;
           case eCSSProperty_resizer:          aValue = mUserInterface->mResizer;         break;
-          case eCSSProperty_behavior:         aValue = mUserInterface->mBehavior;        break;
+          case eCSSProperty_behavior:         
+            aValue = mUserInterface->mBehavior;        
+            break;
 
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
diff --git a/content/html/style/src/nsCSSStruct.cpp b/content/html/style/src/nsCSSStruct.cpp
index 202be1bd68c0..c08f2aa47460 100644
--- a/content/html/style/src/nsCSSStruct.cpp
+++ b/content/html/style/src/nsCSSStruct.cpp
@@ -1610,7 +1610,9 @@ CSSDeclarationImpl::AppendValue(nsCSSProperty aProperty, const nsCSSValue& aValu
             break;
           case eCSSProperty_user_focus:       mUserInterface->mUserFocus = aValue;      break;
           case eCSSProperty_resizer:          mUserInterface->mResizer = aValue;        break;
-          case eCSSProperty_behavior:         mUserInterface->mBehavior = aValue;       break;
+          case eCSSProperty_behavior:         
+            mUserInterface->mBehavior = aValue;      
+            break;
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
       }
@@ -3046,7 +3048,9 @@ CSSDeclarationImpl::GetValue(nsCSSProperty aProperty, nsCSSValue& aValue)
             break;
           case eCSSProperty_user_focus:       aValue = mUserInterface->mUserFocus;       break;
           case eCSSProperty_resizer:          aValue = mUserInterface->mResizer;         break;
-          case eCSSProperty_behavior:         aValue = mUserInterface->mBehavior;        break;
+          case eCSSProperty_behavior:         
+            aValue = mUserInterface->mBehavior;        
+            break;
 
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
diff --git a/content/html/style/src/nsCSSStyleRule.cpp b/content/html/style/src/nsCSSStyleRule.cpp
index 0e91b95333c3..41c14beff657 100644
--- a/content/html/style/src/nsCSSStyleRule.cpp
+++ b/content/html/style/src/nsCSSStyleRule.cpp
@@ -2552,6 +2552,9 @@ MapDeclarationUIInto(nsICSSDeclaration* aDeclaration,
       if (eCSSUnit_URL == ourUI->mBehavior.GetUnit()) {
         ourUI->mBehavior.GetStringValue(ui->mBehavior);
       }
+      else if (eCSSUnit_None == ourUI->mBehavior.GetUnit()) {
+        ui->mBehavior.Truncate();
+      }
 
       // key-equivalent: none, enum XXX, inherit
       nsCSSValueList*  keyEquiv = ourUI->mKeyEquivalent;
diff --git a/layout/html/style/src/nsCSSDeclaration.cpp b/layout/html/style/src/nsCSSDeclaration.cpp
index 202be1bd68c0..c08f2aa47460 100644
--- a/layout/html/style/src/nsCSSDeclaration.cpp
+++ b/layout/html/style/src/nsCSSDeclaration.cpp
@@ -1610,7 +1610,9 @@ CSSDeclarationImpl::AppendValue(nsCSSProperty aProperty, const nsCSSValue& aValu
             break;
           case eCSSProperty_user_focus:       mUserInterface->mUserFocus = aValue;      break;
           case eCSSProperty_resizer:          mUserInterface->mResizer = aValue;        break;
-          case eCSSProperty_behavior:         mUserInterface->mBehavior = aValue;       break;
+          case eCSSProperty_behavior:         
+            mUserInterface->mBehavior = aValue;      
+            break;
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
       }
@@ -3046,7 +3048,9 @@ CSSDeclarationImpl::GetValue(nsCSSProperty aProperty, nsCSSValue& aValue)
             break;
           case eCSSProperty_user_focus:       aValue = mUserInterface->mUserFocus;       break;
           case eCSSProperty_resizer:          aValue = mUserInterface->mResizer;         break;
-          case eCSSProperty_behavior:         aValue = mUserInterface->mBehavior;        break;
+          case eCSSProperty_behavior:         
+            aValue = mUserInterface->mBehavior;        
+            break;
 
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
diff --git a/layout/html/style/src/nsCSSStyleRule.cpp b/layout/html/style/src/nsCSSStyleRule.cpp
index 0e91b95333c3..41c14beff657 100644
--- a/layout/html/style/src/nsCSSStyleRule.cpp
+++ b/layout/html/style/src/nsCSSStyleRule.cpp
@@ -2552,6 +2552,9 @@ MapDeclarationUIInto(nsICSSDeclaration* aDeclaration,
       if (eCSSUnit_URL == ourUI->mBehavior.GetUnit()) {
         ourUI->mBehavior.GetStringValue(ui->mBehavior);
       }
+      else if (eCSSUnit_None == ourUI->mBehavior.GetUnit()) {
+        ui->mBehavior.Truncate();
+      }
 
       // key-equivalent: none, enum XXX, inherit
       nsCSSValueList*  keyEquiv = ourUI->mKeyEquivalent;
diff --git a/layout/style/nsCSSDeclaration.cpp b/layout/style/nsCSSDeclaration.cpp
index 202be1bd68c0..c08f2aa47460 100644
--- a/layout/style/nsCSSDeclaration.cpp
+++ b/layout/style/nsCSSDeclaration.cpp
@@ -1610,7 +1610,9 @@ CSSDeclarationImpl::AppendValue(nsCSSProperty aProperty, const nsCSSValue& aValu
             break;
           case eCSSProperty_user_focus:       mUserInterface->mUserFocus = aValue;      break;
           case eCSSProperty_resizer:          mUserInterface->mResizer = aValue;        break;
-          case eCSSProperty_behavior:         mUserInterface->mBehavior = aValue;       break;
+          case eCSSProperty_behavior:         
+            mUserInterface->mBehavior = aValue;      
+            break;
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
       }
@@ -3046,7 +3048,9 @@ CSSDeclarationImpl::GetValue(nsCSSProperty aProperty, nsCSSValue& aValue)
             break;
           case eCSSProperty_user_focus:       aValue = mUserInterface->mUserFocus;       break;
           case eCSSProperty_resizer:          aValue = mUserInterface->mResizer;         break;
-          case eCSSProperty_behavior:         aValue = mUserInterface->mBehavior;        break;
+          case eCSSProperty_behavior:         
+            aValue = mUserInterface->mBehavior;        
+            break;
 
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
diff --git a/layout/style/nsCSSStruct.cpp b/layout/style/nsCSSStruct.cpp
index 202be1bd68c0..c08f2aa47460 100644
--- a/layout/style/nsCSSStruct.cpp
+++ b/layout/style/nsCSSStruct.cpp
@@ -1610,7 +1610,9 @@ CSSDeclarationImpl::AppendValue(nsCSSProperty aProperty, const nsCSSValue& aValu
             break;
           case eCSSProperty_user_focus:       mUserInterface->mUserFocus = aValue;      break;
           case eCSSProperty_resizer:          mUserInterface->mResizer = aValue;        break;
-          case eCSSProperty_behavior:         mUserInterface->mBehavior = aValue;       break;
+          case eCSSProperty_behavior:         
+            mUserInterface->mBehavior = aValue;      
+            break;
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
       }
@@ -3046,7 +3048,9 @@ CSSDeclarationImpl::GetValue(nsCSSProperty aProperty, nsCSSValue& aValue)
             break;
           case eCSSProperty_user_focus:       aValue = mUserInterface->mUserFocus;       break;
           case eCSSProperty_resizer:          aValue = mUserInterface->mResizer;         break;
-          case eCSSProperty_behavior:         aValue = mUserInterface->mBehavior;        break;
+          case eCSSProperty_behavior:         
+            aValue = mUserInterface->mBehavior;        
+            break;
 
           CSS_BOGUS_DEFAULT; // make compiler happy
         }
diff --git a/layout/style/nsCSSStyleRule.cpp b/layout/style/nsCSSStyleRule.cpp
index 0e91b95333c3..41c14beff657 100644
--- a/layout/style/nsCSSStyleRule.cpp
+++ b/layout/style/nsCSSStyleRule.cpp
@@ -2552,6 +2552,9 @@ MapDeclarationUIInto(nsICSSDeclaration* aDeclaration,
       if (eCSSUnit_URL == ourUI->mBehavior.GetUnit()) {
         ourUI->mBehavior.GetStringValue(ui->mBehavior);
       }
+      else if (eCSSUnit_None == ourUI->mBehavior.GetUnit()) {
+        ui->mBehavior.Truncate();
+      }
 
       // key-equivalent: none, enum XXX, inherit
       nsCSSValueList*  keyEquiv = ourUI->mKeyEquivalent;