I've notice that there are two different methods of quantifying the layout in CSS, that is by percentage and pixels. I know that it depends on which one that is being used, it would change the layout. Under which circumstance should one be used over another and is there a uniform standard if there is a preference?
For responsive design for example, using percents is the way to go, as elements having, say, a
width: 50%; will always use half the container on any device, whatever the size, as opposed to, say,
width: 400px; which would be messed up in a small size device.
But of course sometimes you want to use pixels to define an element to always have a fixed width. It really depends on the use case. But the main thing to have in mind is how the element will adjust in different screen sizes.