html - CSS Selectors to Apply Border to h4 -

on http://adasportsandrackets.com/wordpress, trying add css add border under h4 heading "best sellers." it's not working , it's not caching issue i've tried in major browsers after deleting cache.

here html:

<div class="wpb_text_column wpb_content_element  best-sellers"> <div class="wpb_wrapper"> <h4>best sellers</h4>  

and here css:

.best-sellers h4 {  border-bottom: 1px solid #eee; padding: 7px 0px;  } 

i tried:

.best-sellers {  border-bottom: 1px solid #eee; padding: 7px 0px;  } 

this worked me:

.page-template-template-home-default-php .wpb_wrapper h4 {     border-bottom: 5px solid #999; } 

or try:

.best-sellers h4 {border-bottom: 5px solid #999;}