There is a limited amount of storage space on those sites (which is why there are two). Please don't post your highest resolution pics, which take lots of space and can't be seen without scrolling sideways anyway: resize them to about 800-1000 pixels wide which is a good compromise between storage space and ability to see plenty of detail.
And if you already have pictures up there, please take a look at yours and check on the sizes. You can delete the high-res space-hogging versions and leave the smaller sizes for everyone to enjoy.