Expression Should Be Escaped warning is issued in the following situation:
The expression contains '<script>'. Consider setting the 'Escape Content' property to 'No' or the expression will be displayed as text
Your expression contains an HTML tag, so it is probable that you want to render the expression as HTML instead of text.
Change the 'Escape Content' of the expression property to 'No' to render the expression as HTML, or leave it as 'Yes' if you want to display the expression as text.