i'm just wondering since they sell batteries at the junk yard, are they still good to use? i was short on money and bought one for $20 at the junk yard since the one in my car got tested bad when i brought it to autozone. my car still doesn't start though so i'm not sure if the battery from the junk yard was defective also or there's just another problem to my car ;\

 

well you really cant tell. you put a suspect battery in the car.
if you can get the car to a shop, do a starter draw test and see if thats it, a voltage drop test.

first make sure all your connections are good.

 

my connections are good. its cranking but not turning on. i hear the starter click once or so.. the day before it stopped turning on i heard something sputtering like struggling to turn on. after that it just stopped turning on

 

so the engine is cranking, and sounds like it has compression?
if thats the case, you need 4 things for an engine to run
1-air 2-fuel 3-compression and d-correct ignition timing
so go from there.