This question already has an answer here:
Today I was using the graph located in the reputation tab for my own profile in Stack Overflow:
As you can see it says
select an area by dragging across the lower chart
But nothing happens if try to drag or click anywhere in the lower chart. I didn't know if this was something I was not understanding and so I tried the same in my profile at https://apple.stackexchange.com/ as follows:
As you can see, there I can click and drag to select and area and it works just fine.
Just tried with Firefox and it works fine. I use google chrome and it does not work even if I try with a new incognito window. I have Ubuntu 12.10 if it matters. Chrome version: Version 40.0.2214.93 (64-bit)