Hello, I have this script that takes input from three form boxes and inserts it into a mailto href. but when i try to modify it at all it stops working. what i want to do is have if, else, and if else statements that if a user doesnt fill in a box it alerts them what box they didnt fill in and goes back to the input boxes so they can fill it in. ive tried many times to do this but it seems that every time i touch it it messes up

Here is the code

Code:
<script type="text/javascript">
function email (form) {
var address = form.address.value;
var name =form.name.value;
var username = form.username.value;
today = new Date();
BigDay = new Date("December 25, 2008")
msPerDay = 24 * 60 * 60 * 1000 ;
timeLeft = (BigDay.getTime() - today.getTime());
e_daysLeft = timeLeft / msPerDay;
daysLeft = Math.floor(e_daysLeft);
e_hrsLeft = (e_daysLeft - daysLeft)*24;
hrsLeft = Math.floor(e_hrsLeft);
minsLeft = Math.floor((e_hrsLeft - hrsLeft)*60);
document.location.href = "mailto:" + address + "?subject=Whatever&body=Hello " + name + ",<br><br>" + daysLeft + " days, " + hrsLeft + " hours and " + minsLeft + " minutes left. This message was sent to you from " + username + "
}
</script>
Code:
<form name="info" method="get">
<input type="text" name="address" value="Recipiant's E-mail Address" onclick="this.value='';this.onclick=null;" /><br />
<input type="text" name="name" value="Recipiant's Name" onclick="this.value='';this.onclick=null;" /><br />
<input type="text" name="username" value="Your Name" onclick="this.value='';this.onclick=null;" /><br />
<input type="button" name="button" value="Tell A Friend" onclick="email(this.form)" />
<input type="button" name="button" value="Reset" onclick="javascript:if(confirm('Are you sure you want to reset the info?')) { document.info.reset(); }"/>
</form>