ZenitPCB
Free PCB Layout for your electronic projects...
ZenitPCB
Stortini Mirko Bruno
Design Rule Checker  &  Net Classes
Copyright 2006-2012 by
"ZenitPCB Layout"
All Rights reserved
info@zenitpcb.com
Elements checked :
Clearance between electrical elements E-E :
Trace-Trace | Trace - Pad | Pad - Pad | Trace - Slot
Clearance from electrical elements and board outline B-E :
Trace-BoardOutline | Pad-BoardOutline
Clearance from electrical elements and e Mounting Hole M-E :
Trace - MHole | Pad - MHole
Clearance from electrical elements and Copper Pour C-E :
Clearance between components C-C :
Overlap of the text on the pad X-E :
DRC Settings
Different  Top-Bottom Clearance
DRC Example :
O
Text (SilkScreen) over a pad.
O
Collision between components
Net  Classes

ZenitPCB Layout may assign to each net, a design rule that is enclosed in the "Net Class.

Each class can set the width of the trace ( Min - Typical - Max )

Furthermore you can set the clearance between the elements : 
Pads-Pads \ Pads-Trace \ Trace-Trace and electrical elements\Copper Pour.

You can set a default via which will be used for the automatic via placement and color connections.
You can save a NetClasses setting file .
After creating the net class you can "join" each net with a class ( Net Property ).
e.g. net $GND you can assign the net class "GND".