I uploaded my image and all that appeared was a red X....Why?

The site automatically resizes images. If you upload a really huge image then the site cannot resize this. The site will end up posting a red x out of frustration :(

I saw this happen with an image that was 2000 x 2000 pixels.

To fix this issue, just use any image editor to reduce the size of the image to something in the neighborhood of 500 x 500 pixels and then the site can resize the image as desired.