Long pages in FireFox offset when scrollbar appears

Question

In Firefox and Safari, pages that are centered move a few pixels when the page is long enough for the scrollbar to appear. If you navigate through a site that has long and

Answer 1

You could simply always enable the scrollbar:

html{
 overflow: scroll;
}

but that would give you the horizontal scrollbar too, this is better:

html{
   overflow-y:scroll;
   overflow-x:auto;
}

That will give you only the vertical scroll and the horizontal when needed.