Grinvik.Com

HTML

<input id="fontSize" type="checkbox" value="10px"/> font-size

JavaScript

document.getElementById('fontSize').onclick=function(){addingStyle(this.id,this.value)}
var clickNumber=0
function addingStyle(property,value){
	var html=document.documentElement.style
	if(clickNumber%2===0)html.fontSize=value
	else html.fontSize=''
	clickNumber++
}