validate input values

[earl]

Hey,

I've made a form with bunch of data the user needs to register, looks
something like this,
<form action="register.asp" method=post>
<table width="400" border="0" align="center" cellpadding="0"
cellspacing="0">
<tr>
<td align="left"><b>Name</b></td>
<td align="left"><input name="name" type="text" size="30"></td>
</tr>
<tr>
<td align="left"><b><p>Date</b></td>
<td align="left"><input name="birthdate" type="text" size="30"></td>
</tr>
<tr>
<td align="left"><b><p>phone number</b></td>
<td align="left"><input name="phone" type="text" size="30"></td>
</tr>
</table>
<input type="submit" value="Submit" name="button">
</form>

How can I validate what the user actually inputed a number in the phone
number box and a date with the proper format in the date input box before
the form is submitted ?

Appreciate any help.