help-- noobie illustrator vector question

[Mondatta]

Thanks so much for helping a newbe with this *very* frustrating
issue. I understand that vector graphics are the best to use because
you can blow them up huge.

My problem:
-I have autotraced a logo using vector graphics in illustrator. It
looks smooth even when zooming in at the largest setting
When I export this to put it in a website, it looks jagged again-- no
smoothness. I have tried .png and jpeg. I have also tried to work
with Microsoft Expression studio and the logo is perfectly smooth in
there until I try to save it in another format. The logo looks jagged
even when I import it into illustrator using .png. However, it looks
FINE in expression studio.

Soo-- why do my images in illustrator/expression studio have the
jaggies when I save and view them, even when going to another vector
program (illustrator to expression studio). Keep in mind they look
perfect in the program? THANKS SO MUCH IN ADVANCE!