Sorted:

Help with undefined index in PHP?-Collection of common programming errors

Using properties defined in the Options constructor within custom methods in mootools-Collection of common programming errors

codeigniter database error in selecting data-Collection of common programming errors

problem about nm-Collection of common programming errors

Why doesn't Mathematica use uniform criteria for validating Options?-Collection of common programming errors

problem about lex-Collection of common programming errors

Slope-intercept equation?-Collection of common programming errors

Why can't I e-mail people ?-Collection of common programming errors

If the derivative of an equation is undefined at one point, what is happening at that point?-Collection of common programming errors

PhP Undefined Variable?-Collection of common programming errors