how to hide div in html

1document.getElementById('elementName').hide();

1#elementID{
2display:none;
3}

1<div id="main"> 
2  <p> Hide/show this div </p>
3</div>
4
5('#main').hide(); //to hide
6
7// 2nd way, by injecting css using jquery
8$("#main").css("display", "none");