[TYPO3-english] Frontend pages show 404 error, viewing in the backend works fine

[Jennifer Koenig]

I've got my introductory package Typo3 site up and running and can log into the backend just fine.  However, from the front end, when I click on any of the navigation links, I get sent to an address like:

mysite/examples

which gives me a 404 "file not found" error.

In the backend, though, all of the pages that correspond to the navigation links are there, and I can view them just fine.  The address in the browser is

mysite/index.php?id=4

So I'm guessing that there's some kind of routing problem that I need to fix - in an ._htaccess file?  Is there a Rewrite directive that I'm missing, or could the problem be somehwere else?  In the Install Tool, everything is "green" and seems to be configured correctly.  mod_rewrite is enabled in Apache, as well.