To get size of visible area of HTML page
window.innerHeight
window.innerWidth
document.body.clientHeight
document.body.clientWidth
document.documentElement.clientHeight
document.documentElement.clientWidth
To get height - width of user screen
screen.height
screen.width
To get height - width of HTML document
document.body.scrollHeight
document.body.scrollWidth
Set opacity of a HTML element using JavaScript
document.getElementById('<id-of-element>').style.MozOpacity=.80
document.getElementById('<id-of-element>').style.opacity=.5
document.getElementById('<id-of-element>').style.filter="alpha(opacity = 50)";
Remove HTML Document Scroll bars
document.body.style.overflow="hidden"
Get Size of and HTML Element
document.getElementById('<id-of-element>').clientHeight
document.getElementById('<id-of-element>').clientWidth
Delete or Remove an element from HTML Document
document.body.removeChild(document.getElementById('<id-of-element>'))
