Jonthue Michel1,462 Points
So wouldn't pxiel length values be more mobile friendly than px?
What would be the need for px if its better to use percentages for total flexable site?
Kevin Korte28,082 Points
As you'll learn, there will be times when you don't want things to change by percentages. A rough and dirty example is let's say you had a two column layout. The total of the two columns could be 80% of the screen width, and each column could be 30% of the screen width, but if the distance between the two columns was something like 5%, on a large screen that might be 40 or 50 pixels, which would look weird. In that case, it might not be a bad idea to fixe the distance between the two columns at 10 or 15 pixels and let everything else around it grow as the screen size does.
Lots of other examples, but that's just one.