Solved: why can't my web page be found?

The place I teach requires us the instructors to create our own sub-web page. I created a page called "WCmain.html" I put a link there under my class, but it cannot be found. Could you tell me what the problem is?

Since my page is in the same DIRECTORY as CLASSES.PHP. I did not type any http://, since my page should be under the root directory.

Would you check this website http://www.artworksonthesquare.com? Click on "Classes" tab. Find the Tuesday Classes and find Watercolor painting with Judy Huang. I insert my web page on "Click Here."

Thanks

 

Thank you, cwwozniak. I finally figured that the website builder automatically added php as a file extension.