Question

Considering a document with font-size set to a combination of pixels, % and keywords(x-small, etc). Is it possible to increase the font-size for all those elements at the same time?

Something like $("*").each(function(){$(this).increase_fontsize();}?

Answer 1

Using em and % its possible..

For example set a parent div font size to 100% from css and update font size from javascript.

Ex:

#sample
{
font-size: 100%;
}

#sample > .child{
font-size: 1em;
}

increase/ decrease the font-size from javascript

JSFiddle: http://jsfiddle.net/Scrtr/2/