When I open IE it says error 404
Depending on the site, you may get a browser error saying 404 page not found
or a friendlier message from the site itself.
They both mean the URL you’ve typed doesn’t link to a page.
Check your typing and try .htm instead of .html. If you followed a link there, go back and see if you can find another way in. If all links give you "not found" there’s an error on the site and you might want to email them about it.