Lightly touch the contest box and you'll then see the "X" to close it.
or stop using your phone as a computer replacement.
It'd take 20 minutes to scroll to a corner to close it -- that thing is HUGE!
This is on my desktop with a 23" screen.
I found in a support forum what the problem probably is: some fast-and-dirty code used by spammers to avoid pop-up blockers doesn't play nicely with disability-assist software even when the site is whitelisted.
From the level of snark in your post, I guess you now think I should apologize for being disabled and needing to use Google/IE/Edge/Firefox-compatible assistance software to view websites because it means I can't revel in your shoddily-coded advertisements.