Stacking of items

i wonder how will i know if the items of my map can or cannot be stack?
because one guy complain to me that my items stack but i tried to look at the map editor and i could't find any option related to it.

Orb effects and Arrow-style abilities don't overlap in effect. Some poisons do, some don't. Everything else that I know of stacks.

How about critical ability + critical items?

boots of speed + endurance or unholy aura?

Critical strike items do stack with the ability. I remember seeing a hero with the ability and 2 items and doing totally different damages from 50s to 300s right after each other.

yes, Critical Strikes stack, each time the unit attacks each critical strike ability runs, so if u have 6 critical strike items its possible for all 6 of them to hit at once, making uber damage.

Also, to my knowledge, critical strikes can stack with other "orb abilities", well, actually, with up to 1 orb ability (because the orbs themselves don't stack). Mask of death and various "arrow" abilities work as "orb" abilities as well, but I think slow poison doesn't and can be used in conjuction with any other orb (not sure though).

Oh, and multiple boots of speed don't stack (their abilities that increase the speed by a fixed value, abilities that increase the speed by percentage stack, I think). Same auras don't stack as well, but if you use two different auras and boots of speed, they will all stack.

Mask of death stacks with other masks of death, at least it used too. I remember i used to play hero arenas with 6 masks of death for a 300% Hitpoint gain on a fast attacking agil based hero, damn that was great fun :D