html - Fieldset and legend tag does't work in asp.net mvc -

i've used master page (.cshtml page) , sub page (.cshtml page) under master page. when use <fieldset></fieldset> & <legend></legend> tag inside sub page shows horizontal line instead of actual output of <fieldset></fieldset> & <legend></legend> tag. how can solve it?

this master page

this sub page

go views>shared>_layout.cshtml. comment --> @styles.render("~/content/css") . work