I found a bottle of pills and would like to know what they are they are white with imprint of a236 on them

Please take them to your pharmacist for identification and disposal.

It's Acetaminophen with Butalbital plus cafeine: A pain reliever / fever reducer with cafeine to prevent drowsiness. However it's not sold in the US anymore so if your from the US, the bottle is probably very old and should be tossed.

acetaminophen and butalbital Drug Information (http://www.drugs.com/mtm/acetaminophen-and-butalbital.html)