Echo url in error log file

[eluser]df_phot[/eluser]
I've been loggin my errors for several weeks now and I consistently get a particular 404 error. I can't figure out where this bad URL is coming from and why it happens so frequently. Is there a way to have the error logs echo the URL of the page where it occurred at? If so, that would help tremendously. Thanks in advance for the help!

[eluser]tomcode[/eluser]
show_404() takes a parameter which is logged ...

Code:

show_404($this->uri->uri_string());

[eluser]df_phot[/eluser]
I did a search and found 'show_404' in 5 different files. Which one do I alter?

[eluser]tomcode[/eluser]
Well all of them ... and if You want to trace down the call :

Code:

show_404('show_404 #1 ' .$this->uri->uri_string()); // #2, #3 ...

[eluser]df_phot[/eluser]
Thanks for pointing me in the right direction. I guess I realized (after the fact) what I meant to ask. I meant to ask what the referring site is. Then I found <a href="http://ellislab.com/forums/viewthread/51610/">this thread</a> that shows how to do it. Thanks!