When some people upload avatars, they get this error;

All hope is lost, right? Make it smaller even though you've made it as small as you possibly could? Nope, it's the complete opposite.
Step 1 (I'm using gimp for this so you might as well just install it because I haven't done this on Paint.net or anything):Open your avatar that isn't working
Step 2:Export as PNG by going to file and export, make sure it's png so this pops up:
Step 3:The thing we're focussing on is the Compression level slider.

Slide it down to zero.
It should work, it's what I've done to fix my issues.
I wasn't sure where to put this but I wanted to help people.