It seems there are many searchers complaining in the Google Web Search Help forums that the back button is malfunctioning on Google search. Searchers are saying that when they click it, it leads to a blank page and they cannot do anything afterwards.
The first reports of this came a few weeks ago but I have yet to see a Googler respond to it. I know Google is aware of it, since the top contributors there have “escalated” the issue with them back on July 3rd but the issue still is happening for many searchers.
Here is a screen shot of what some of these searchers see after they click the back button:
Some are saying this is limited to Internet Explorer 11, but I am again not sure.
Forum discussion at Google Web Search Help.