I asked a question [here][1] looking for design ideas for an alternative to the nested drop-down menus scheme I had come up with.  User mikryz helpfully provided an alternative idea with this mockup:

[![enter image description here][2]][2]

I'm having trouble figuring out what to display on the left hand side when a user first visits the site and has not selected a "report category" from the top "Reports" drop down menu at the top.

The two ideas I had were to display a vertical bar from top to bottom with the same color as the navigation bar but with nothing in it.  Then populate it upon the event.  I don't like this idea because I don't want a dark background underneath the content (the nav bar color must stay the same).

The other idea I had was to have the content slide in from the left when the user clicks a Report category.  However, I'm still unable to find a way to get it to slide in **underneath** the navbar instead of pushing the navbar to the right as well (I'm using Bootstrap 3).  I know this is a UX forum and not primarily a developers or BS3 forum so I am not holding out hope for help solving this.  Suffice to say I've googled for hours without solution.  SE prevents me from posting a link to the "answered" solutions to this problem that did not help me.

**My question:  What should I display in an area on initial page load that only contains content after a user makes a selection?**

In particular, looking at the graphic above: what should go on the left-hand side when the page loads for a user but before she has chosen a category of content to display there?

  [1]: http://ux.stackexchange.com/questions/89476/how-to-display-nested-categories-of-data-without-using-nested-menus
  [2]: https://i.sstatic.net/c0PGk.png