Help adding field box text to Search Form

I have this Form code that works successfully to Search a web site (below).
How can I add text in the field/box that will disappear when the field/box is selected to add search keywords to?
Also, how can I widen the field/box?
Any help/examples/suggestions will be appreciated.

<form method="get" action="search.php">
<div id="siteSearch">
Enter Search Words <img src="themes/default/images/arrow-red.png">&nbsp;&nbsp;
<input type="hidden" name="type" value="videos"/>
<input type="text" name="keyword" id="sbi1" value="" onfocus="if(this.value==this.defaultValue) this.value='';">
<input type="image" align="middle" src="images/search.png"  name="sa" value="Search" id="mySearch"/><br/>
</div>
</form>

You can widen the size of a text box with css and changing the width attribute. You can also add in size=“30” attribute if you don’t want to use css.


if(this.value==this.defaultValue) this.value='';

Not sure what the above is for; is that you trying to remove any placeholder text when the user clicks on the input?