I am making custom monsters for my server but I forgot how to add extra gold to the monster corpse... plz help!

How do you want to do it - by modifying/creating the creature script itself or by adding it to specific spawned creatures through a spawner specification or attachment?

makeing a totaly custom creature by useing xmlspawners ... i guess it would look like Rat/name/namehere/hue/huehere/ i wanna add gold to it but i forgot how.

rat/name/blah/ADD/gold,500

will add 500 gold to the creature when spawned.
The ADD keyword is used to add stuff to containers or creatures when spawned.
The constructor for gold accepts a quantity argument, so you can pass that argument to the constructor with "gold,500" to add a stack of 500 gold.