CSS Header style not applied to children

I am beginner to UI World, trying to style and arrange html components in one of my example, but I could not see the style applied for all the children of HTML header component. Here is what I have tried Demo in JsFiddle

Code :

<header class="page_header_style">
     <div>
         <div class="title_style">
             Main Title
         </div>
         <div>
            <ul class="user_style">
                <li>Welcome Srk</li>
                <li><a href="">Logout</a></li>
            </ul>  
          </div>    
     </div>
</header>

I would like to see the second div i.e., Welcome message & a list in the same line of the title.