HTML Code:
<script type="text/javascript">
<!--Hide from old browsers
var today = new Date();
var dayofweek = today.toLocaleString();
var dayLocate = dayofweek.indexOf(" ");
var weekDay = dayofweek.substring(0, dayLocate);
var newDay = dayofweek.substring(dayLocate);
var dateLocate = newDay.indexOf(" ");
var monthDate = newDay.substring(0, dateLocate+1);
var yearLocate = dayofweek.indexOf("2010");
var year = dayofweek.substr(yearLocate, 4);
var springDate = new Date("March 21, 2010");
var daysToGo = springDate.getTime()-today.getTime();
var daysToSpring = Math.ceil(daysToGo/(1000*60*60*24));
document.write("<p style=\"margin-left:10%; font-family:Arial, sans-serif; font-weight:bold; font-size:14\">Today is "+weekDay+" "+monthDate+" "+year+", that leaves only "+ daysToSpring +" days until the start of spring.")
document.write("<br />Spring is the time to prepare your landscape for new growth of flowers and lawns. ")
document.write("<br />Call us now at (221) 555-9100 for a free consultation and free eestimate.</p>")
//-->
</script>
You need to escape " and you had a typo... monthDay? monthDate?