Changing length of Navigation Bar made with CSS - html

Question

Is it possible to change the length of a navbar made by CSS? If so, how is it done? Like instead of stretching across the whole page, it stops at a certain distance
Here is a JSFiddle to illustrate the sidebar, aka the distance i need the navbar not to cover http://jsfiddle.net/jAVQv/
Here is the code that I have for the navbar (from W3Schools with minor edits):
ul.topnav:not(.ignore) {
list-style-type: none;
margin: 0;
padding: 0;
overflow: hidden;
background-color: #333;
}
ul.topnav li:not(.ignore) {float: right;}
ul.topnav li a:not(.ignore) {
display: inline-block;
color: #f2f2f2;
text-align: center;
padding: 14px 16px;
text-decoration: none;
transition: 0.3s;
font-size: 17px;
}
ul.topnav li a:hover:not(.ignore) {background-color: #555;}
ul.topnav li.icon {display: none;}
#media screen and (max-width:680px) {
ul.topnav li:not(:first-child):not(.ignore) {display: none;}
ul.topnav li.icon:not(.ignore) {
float: right;
display: inline-block;
}
}
#media screen and (max-width:680px) {
ul.topnav.responsive:not(.ignore) {position: relative;}
ul.topnav.responsive li.icon:not(.ignore) {
position: absolute;
right: 0;
top: 0;
}
ul.topnav.responsive li:not(.ignore) {
float: none;
display: inline;
}
ul.topnav.responsive li a:not(.ignore) {
display: block;
text-align: right;
}
}