An Odd Question About Posting Pictures

[Wagriff]

I've noticed that Some photos that a person posts will enlarge when clicked on and some do Not. I have no problems at all with the Forum Photo Uploading-it's simple enough-just 1-2-3 and you're done. But why do some photos have the ability to be enlarged and some don't? Not a huge problem,of course, but just one that I noticed. Dimas? Anyone?

[youthcollector1]

Could be a few things such as, size, format, way in which it's upload, etc..... I'm positive exactly why it does it here, but I've notice it, too.