【求助】在input标签中使用if标签报错

<select name="target" size="1" id="target">
<option value="_blank" <if condition="$vo.target eq *_blank*">selected=*selected*</if>>_blank</option>
<option value="_new" <if condition="$vo.target eq *_new*">selected=*selected*</if>>_new</option>
<option value="_parent" <if condition="$vo.target eq *_parent*">selected=*selected*</if>>_parent</option>
<option value="_self" <if condition="$vo.target eq *_self*">selected=*selected*</if>>_self</option>
<option value="_top" <if condition="$vo.target eq *_top*">selected=*selected*</if>>_top</option>
</select>