webgl,opengl es 2.0 and texture atlas

I would create a texture atlas render sistem for my sketchup importer , my problem is to size the max of width and height of the texture atlas for webgl , that uses opengl es 2.0 (is true?).

There are some constraint in webgl for the width and height of a texture ?
and a size constraint?

i wish visualize the imported model from sketchup ,if is possible, on iphone or ipad.