Onclick event

onClick sets a script to run when the user clicks on
the link.For example, this link creates an alert box which
says Heading Home! when the link is clicked:



<A HREF="mypage.oc.html" onClick="alert('Heading Home!')"
>My Page</A>

One of the more useful uses of onClick is creating a popup window
which the links targets. This example uses our popup window script
<A

HREF="mypage.popup.html"

onClick="return openWindow(this,'mypage')"

>My Page</A>

If onClick returns
a value of false then the click is cancelled and the browser doesn't
go anywhere. For example, you could check if a user really wanted
to go to a URL like this:

<A >
    HREF="deleted.oc.html"
    onCLick="return confirm('Are you SURE you want
                to delete this record?')"
    >Delete It!</A>

source : http://www.idocs.com/tags/