I'm presenting this as a workaround rather than a solution. This may not work all the time. I did it this way as I'm doing a very basic HTML page, for internal use, in a very bizarre environment. I know there are libraries like MaterializeCSS that can do really nice nav bars. (I was going to use them, but it didn't work with my environment.)
<div id="nav" style="position:fixed;float:left;overflow-y:hidden;width:10%;"></div>
<div style="margin-left:10%;float:left;overflow-y:auto;width:60%;word-break:break-all;word-wrap:break-word;" id="content"></div>