This question already has an answer here:
I am working on a project similar to the one at http://www.instructables.com/id/Raspberry-Pi-Wall-Mounted-Google-Calendar/?ALLSTEPS
Similarly, I need my pi to stay on constantly. I have the regular Raspbian OS installed and I am using Iceweasel browser to run a web application all day.
I have tried every single one of these suggestions from this link http://www.bitpi.co/2015/02/14/prevent-raspberry-pi-from-sleeping/
Yet the pi fails to stay on longer than 10 minutes. Any help would be greatly appreciated.