What is actual pixel size of output page in this app?

Answer 1

"Pixel size" depends of hardware display devices, not software at all... ( even if management of virtual pixels is sofware ^^ )

Answer 2

Look at css media queries, and associated search to responsive design...
You can start with: http://www.quirksmode.org/blog/archives/2010/09/combining_meta.html

And this last link is usefull for testing device / demonstrating media queries and co': http://mydevice.io

Answer 3

My ppi is about 400 and my screen is 1920/1080, but my question is about when enter some html elements size in px, what screen limit do I have