Indicates a property that expects an expression value.
<se:if expression="3*2==6">equal</se:if>
You should not use a viper with curly baces as an expression value.
Bad syntax: <se:if expression="{html.isselfclosing('br')}">selfclosing</se:if> Correct syntax: <se:if expression="html.isselfclosing('br')">selfclosing</se:if>