Help with some error messages

I am having trouble with a module (see this thread) and need to figure out what some of the error messages I've been getting mean, so I can get to the bottom of my problem by sorting out what doesn't apply.

I've had the debugging error log installed for only 24 hours, only have one error, any idea how to fix?

[11-Jul-2009 06:43:50] PHP Warning: Division by zero in /home/lankyliz/public_html/includes/modules/order_total/ot_group_pricing.php on line 79

Also on my server's error logs, I get the following 2 errors repeated a LOT:

[Sat Jul 11 19:38:36 2009] [error] [client 65.55.211.124] File does not exist: /home/lankyliz/public_html/404.shtml
[Sat Jul 11 19:38:36 2009] [error] [client 65.55.211.124] File does not exist: /home/lankyliz/public_html/robots.txt

Some specific ones I was wondering about:

[Fri Jul 10 19:30:24 2009] [error] [client 76.67.82.122] File does not exist: /home/lankyliz/public_html/\xe2\x80\x9djavascript:;\xe2\x80\x9d, referer: http://lankylizards.com/index.php?main_page=product_info&cPath=14_35&products_id=399

and

[Fri Jul 10 17:37:44 2009] [error] [client 76.173.156.215] File does not exist: /home/lankyliz/public_html/registry.php&zenid=ce3fc1bbc67e535fc18978ca9dda1a99, referer: http://www.lankylizards.com/

And these two:

[Fri Jul 10 11:29:58 2009] [error] [client 76.67.82.122] File does not exist: /home/lankyliz/public_html/404.shtml, referer: http://lankylizards.com/registry.php?create=1
[Fri Jul 10 11:29:58 2009] [error] [client 76.67.82.122] File does not exist: /home/lankyliz/public_html/posh, referer: http://lankylizards.com/registry.php?create=1

I figure I should probably stop there. :P
Any help is greatly appreciated!

laurahowes:

I've had the debugging error log installed for only 24 hours, only have one error, any idea how to fix?

[11-Jul-2009 06:43:50] PHP Warning: Division by zero in /home/lankyliz/public_html/includes/modules/order_total/ot_group_pricing.php on line 79
http://www.zen-cart.com/forum/showpost.php?p=487733&postcount=10

THANKS! Done.