John Andrews over at Johnon.com has an insightful quiz about URL’s.
Q: How many web resources are represented by the following list of URLs, according to Google?
9. www.example.com/index.html (or index.php or index.asp, your web server’s default)
13. http://www.example.com/index (your web server default is still index.html)
Write down which of the above qualify as a web resource. No, don’t click yet to see his answer, write down first.
Done, then go read the article to find John Andrews answer.
After that, start checking your own website.