[gridsix]

I have a form that works when you click the submit button, but does not function when the user hits the 'enter' key. Here's the code:

<form action="index.php" method="get" name="search">
<table border="0" cellpadding="3" cellspacing="2">
	<tr>
		<td align="right">Zipcode: <input name="zipcode" type="text" class="textbox" value="<?=$zipcode;?>" size="8" maxlength="8"/></td>
		<td><input type="button" value="Click to Get Gas Prices" onclick="dosearch(this.form);"/></td>
	</tr>
</table>
</form>

Thoughts?