Question

Whenever i try to make a div with width 100%, it does not go across the whole page, it leaves small margins on either side(top bottom left and right), i would like the div to go across the whole page, such as the header bar on the top of this page.

Answer 1

You have to set margin and padding of body element to 0. Like this (in CSS):

body
{
  margin: 0;
  padding: 0;
}

And also remember about setting margin of div element to 0.