Undifined Indexes

I'm not sure if this is a Xaraya setting or a php_ini setting and I'm 
not seeing anyone else having this issue, but, I've got errors turning 
up "Undefined Index" errors. I know PHP can over look these, and I've 
tested to make sure that I can have a normal PHP page ignore instances 
where the index is undefined, however in my Xaraya site this throws an 
error. Is there a setting somewhere that I'm missing where this can be 
turned off, or are there dire consequences for doing so? I'd like to 
catch these, however I'd rather not have the user bothered with them 
when it's really not important to the working of the program.

Thanks in advance for your help :).

Mike