sidebar bumps to bottom sometimes

can’t figure out why my sidebar sometimes bumps all the way to the bottom below all main content. the weird thing is it does not happen all the time… only occasionally

and it only happens on the single.php pages

any clue why ?

https://www.bestonlinetrades.com/20100524/i-just-went-long-the-united-states-oil-fund-lp-etf-uso/

does anyone else see the sidebar bump to the bottom?

i am using google chrome, but have not so far seen the sidebar bump to the bottom in either firefox or the lastest IE