Do i put the heating mat at the bottom of vivarium or under it? its glass and standing on a wood stand.?

Answers:
Under on side of tank. The other side is for your pet to cool off.

---

Heating mats always go under the tank not inside.. For one main reason they get really warm and a reptile can actually burn his underside by lying on it and another you do not have the cord up and out an also if it is an animal that needs to be sprayed for humidity you are not spraying an electrical cord, also if you hae a light source put the heat mat and light source on the same side so there is a cool side and a warm side to the tank also put the water dish on oppisite side of the heat for the same reason so they can go in it to get cool and also water evaporates more on the warmer side, so it will run dry quicker..

---

I would go with, Debbie W's answer, that's the best advise you can get right there!

---

Always put it under the glass NEVER in your tank.

---

Always under...otherwise you'll have a scorched lizzie :(
My mat sits on a 12mm thick piece of polystyrefoam, which protects the wood stand (they usally sell this in the sish section of pet stores). I've found that I don't need to leave my heat mat on for vey long, it heats up very fast and can make the glass bottom of the tank quite hot.
Good luck :)