Might be Maple Bladder Galls.

You can't upload a picture to this forum, you can only link to pictures that you uploaded somewhere else like photobucket.com. You can upload pictures to gallery forums such as the plant clinic and garden gallery.

Here is a link that might be useful: Maple Bladder Gall Mite

Some sort of gall - there are apparently several to choose from! They don't seem to cause enough damage to need any treatment.

Here are some beautiful photos of several types of gall on various types of leaf, including red Pustule galls (Artacris cephalonea) on a maple leaf:

Here is a link that might be useful: Galls on tree leaves

thanks guys , it does look like a gall after looking at both of the web sites. even if i did not found a exact match. thanks as well for he link to photobucket.com it worked, here's one of my pictures.

Here is a link that might be useful:

Also look here under 'Nail Galls'. There's a red nail gall on a lime tree.

Newt

Here is a link that might be useful: More tree galls