For example, from My.SolidWorks, view the "Running at SolidWorks World 2013" post. Click on the link in this post (which brings you to an external site). Click the browser's back button. You're brought back to the My.SolidWorks login page. You should be brought back to the post. Or, the external link should always open in a new tab.
When you open an external link, it will, and should open in a new tab.
On the new tab the Back button should be disabled. The original reader page, the Back button should work. If not, re-post and tell use the browser type and confirm that it's the back brwoser button on the reader view.