Open modal popup in sharepoint using Content Editor webpart.

added refferences: sp.js ,  sp.core.js  ,sp.init.js

function OpenModalDialog()

{

var options = SP.UI.$create_DialogOptions();

options.title = "Modal dialog Title";

options.autosize = true;

options.url=  "http://www.youraddress.com";

options.showClose= true;

options.allowMaximize = false;

 SP.UI.ModalDialog.showModalDialog(options);

}