This onMouseover command is used on the front page the WebMagic Australia site in the subscribe to our email newsletter form. What it does is select a text input box when the mouse is passed over it.   It does this by giving focus on mouse over and selecting on focus.  You could view the source of this page to see how we implemented it within the form or copy the text below:

To grab the script just move your mouse over the text box above and hit CTRL-C then paste it into your HTML document.   As far as I can tell it only works under IE/Netscape 4.0.