If we have two variables A and B, and the both of their values is time, how do we measure the distance between those variables?
Sometime you want to create HTML5 with specific dimension, and then you make browser zooms on it to full screen.
You know HTML pages is static. We can create dynamic website by mixing HTML and another language, such as PHP.
If you have several CSS file as your web theme, then you must allow your user to switch between one of them.