Establishes the text to be displayed in a 'tool tip' popup when the mouse is over the displayed node.
var string = element.title; element.title = string;
button1.title = "click to refresh";
If a node does not have a
title attribute, then the default action is to inherit it from its parent node, which in turn may inherit it from its parent node, etc.
According to bug 264001, setting
title to the empty string triggers the default inheriting behavior. To cancel inheritance, title must be set to a non-empty whitespace string.
<div title="CoolTip> <div title="">mouse over here will popup "CoolTip"</div> <div title=" ">mouse over here will popup nothing"</div> </div>