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If you have the photos on your computer, use the Photo icon underneath the Comment text area to browse to the photos. That should work every time. If the image is large it might look washed out for a minute while it is uploading. Once it pops into full glory it should post just fine. If you have the image on a web service, then all bets are off. It is possible to get them here, but the process will be different and more complicated for each service.

If the dead grass nearby some concrete or asphalt? If so then check for chinch bugs. If you wipe the palm of your hand across the grass, the chinch bugs will flick off in the opposite direction of your movement. You can catch them on a piece of paper and investigate further. If you don't get any bugs, then the heat retained by the concrete or asphalt can cause the grass nearby to become dehydrated.

If the dead grass is not near a heat source, then pictures are more necessary.