How do I remove a section of the border on a div to make left nav look seamless with main content section?

Question

I am trying to remove the left border where the active menu item meets right content div.

See http://d.pr/i/hfRZ+

So it appears the active element is the same as

Answer 1

I've slapped together a demo: http://dabblet.com/gist/3762742

Used :after with 1px width and background-color of parent to overlap the right-box's border.