Why is "cursor:pointer" effect in CSS not working

I messed with my css for hours, changing the positioning and z-index of just about every element on the page. I deleted every other element from the DOM except for the one with the cursor: pointer on hover, and it STILL didn't work.

For me, on Mac OSX El Captain V 10.11, the issue had to do with some sort of interference with Photoshop CC. Once I closed photoshop, the cursor started working again.

Solution for me: Close and reopen photoshop

Short answer is that you need to change the z-index so that #firstdiv is considered on top of the other divs.

cursor:pointer doesn't work when you're using Chrome's mobile emulator.