It seems to me that the projection matrix and the modelview are very similar.
once I tryed this:

glMatrixMode(GL_PROJECTION);
// call identity, setup perspective
gluLookAt(...);// or any other way to set the cam
glMatrixMode(GL_MODELVIEW);
// render something

then I tryed

glMatrixMode(GL_PROJECTION);
// call identity, setup perspective
glMatrixMode(GL_MODELVIEW);
gluLookAt(...);// or any other way to set the cam
// render something

and I noticed they work both.
Is there a good reason or I'm just confused?

tnx