How large can pictures be....

I posted some pictures that I have on Google photo. 

http://cs.finescale.com/fsm/modeling_subjects/f/3/t/173411.aspx

All the 5 pictures were showing in the thread the day I posted it.  However when  I checked the thread the the next day, only the fifth picture remained and previous 4 picutres had an X where the pictures where.

I checked on Google photo, and all the pictures where there, so  I was wondering if the dimension where an issue since I left those fields blank.  I had the constrain proportion box checked.

How do you calculate the dimension of the picutre to post on a thread so there is enough space.  (if that was the issue)?

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