html
<div class="div1">
<div class="div2">Title:</div>
<div class="div3">Test</div>
</div>
css
.div1{
width:500px;
}
.div2{
float: left;
font-weight:bold;
}
.div3{
width: 60%;
float: left;
padding-left: 5px;
border-bottom-style: solid;
border-bottom-color: #DDDDDD;
border-bottom-width: 1px;
}
Example

I want the underline fill all the div1 except div2(“Name:”) which is blank at present.
Thanks!
you can right like this
check the example http://jsbin.com/apudil/4/edit#preview