error in xaml resource

Hi,
In xaml, There is an underline on {TemplateBinding Content} in the following script:
The error is: Property 'Content' was not found in type 'Control'
Do y ou see why?
Note that I can compile but not sure why I get this underline.
Any thoughts please?
Thanks

<UserControl.Resources>
...
...
...
<ControlTemplate x:Key="ToolTipTemplate">
<Border BorderBrush="red" BorderThickness="5" CornerRadius="1" Background="blue">
<ContentPresenter Grid.Column="3"
Content="{TemplateBinding Content}"
ContentTemplate="{TemplateBinding ContentTemplate}"
Margin="1,1,1,1"/>
</Border>
</ControlTemplate>
</UserControl.Resources>

Your <ControlTemplate ...> doesn't have a value for TargetType. In Silverlight 3 this was allowed and inferred to be System.Windows.Controls.Control.

Silverlight 4 doesn't allow the lax attribute and will give you the error you're seeing.

Here's an msdn link that explains: XAML Processing Differences Between Silverlight 3 and Silverlight 4