Which one is correct "in" or "on" ?

Hi

I would say

I checked this site with/using Internet Explorer

I think that most ordinary internet users would, as Optilang says, use 'with' or 'using'.

A specialist, such as a programmer or web site designer, might check what the pages look like.
They would say: "I checked this site in IE."

When speaking of a graphic window or browser, things are 'in' the window, never 'on' it.

for internet, i would say "look it up on internet" not "in" .

untoldpainfor internet, i would say "look it up on the internet" not "in" .