Attribute for `<BODY ...>`
`onLoad = "script command(s)"`

Usage Recommendation
use it, but don't rely on it

We've found out that many people are come to this page looking for a variety of techniques. Some of these techniques properly use onLoad, others don't. Here are some of the objectives, and some links to point you in the right direction. After that we'll describe how onLoad works.

Redirecting the Page: If you want the page to automatically forward somewhere else, use <META ...>. See META for Automatic Refreshing and Forwarding.
Popup Window: onLoad cannot be used to control the size or features of the browser window, such as whether or not the window has a status bar or menus. You can control these features when opening new windows. See the Popup Window Tutorial for ready-to-use scripts and examples.
Running Two Commands When The Document is Loaded: See Running Two (or more) Commands With onLoad
Making the Cursor Appear in a Form Field: See Automatically Putting the Cursor in a Field

The browser triggers onLoad when the document is finished loading. The contents of onLoad is one or more JavaScript commands. So, for example, this <BODY ...> tag tells the browser to bring up an alert box once the page is completely loaded:

this code produces this

<BODY onLoad="alert('hello world!')">
this page

Attribute for <BODY ...> onLoad = "script command(s)"

Attribute for `<BODY ...>`
`onLoad = "script command(s)"`