hi, how to create a validation if a choice has been made by the user? thank you for any ideas..

Code:
<body>
<form name="form1">

<select name="menu1">
<option>Select Item
<option>test1 
<option>test2
<option>test3
</select>

</form>
<input type="submit" name="send" value="Send Details"></p>
</body>