I am trying to create a responsive Web which run on every device, while I was searching related topics. I read so many time of `DPI`, `High DPI`. 
I have read of it & understand that it is really important to design responsive website run on every device beautifully. But My main concern is that **"How to get device dpi & how to apply css (media queries) for that"**. 

After that I have also issue of testing it on so many devices,so is there any tool which can simulate target devices environment for testing the same.