How do I enable the error console?
it depends on the browser you're using. see help section.
some tips are at: http://www.softcomplex.com/support/kb_article.php?ref=6824-QUIZ-7814
The errors are
1. syntax error
2. calendar2 is undefined
3. cal1 is null or not an object.
All the files are together in the same directory which is the root of the default.aspx page.
first take care of the syntax error (it can be the reason for the rest). the error message should give you the line number.
Because your files can have includes and server side code the lines the browser reports may not match the lines you're looking at.
use view->source command of the browser to see the output of your server side script. The line numbers should work fine there.