This javascript cut & paste code snippet takes a series of pre-defined checkboxes and checks, or uncheck them all at once. It can even change each checkbox to the opposite checked, or non checked value. This can be very beneficial to services offering a huge catalog of opt in choices, or sales marker. 

Insert this code into your HEAD of HTML

<!-- // == This Script Free To Use Providing This Notice Remains == // // == This Script Has Been Found In The http://www.DesignerWiz.com Javascript Public Archive Library == // // == NOTICE: Though This Material May Have Been In A Public Depository, Certain Author Copyright Restrictions May Apply == // --><script language="JavaScript" type="text/javascript"> <!-- Begin function checkAll() { for (var j = 1; j <= 14; j++) { box = eval("document.checkboxform.C" + j); if (box.checked == false) box.checked = true; } } function uncheckAll() { for (var j = 1; j <= 14; j++) { box = eval("document.checkboxform.C" + j); if (box.checked == true) box.checked = false; } } function switchAll() { for (var j = 1; j <= 14; j++) { box = eval("document.checkboxform.C" + j); box.checked = !box.checked; } } // End --> </script>

Insert this code into your BODY section

<center> <form name=checkboxform> <input type=checkbox name=C1 checked>C1 <input type=checkbox name=C2 checked>C2 <input type=checkbox name=C3 checked>C3 <input type=checkbox name=C4 checked>C4 <input type=checkbox name=C5 checked>C5<br> <input type=checkbox name=C6 checked>C6 <input type=checkbox name=C7 checked>C7 <input type=checkbox name=C8 checked>C8 <input type=checkbox name=C9 checked>C9 <input type=checkbox name=C10 checked>C10<br> <input type=checkbox name=C11 checked>C11 <input type=checkbox name=C12 checked>C12 <input type=checkbox name=C13 checked>C13 <input type=checkbox name=C14 checked>C14 <br> <input type=button value="Check All" onClick="checkAll()" class="hexfield1"><br> <input type=button value="Uncheck All" onClick="uncheckAll()" class="hexfield1"><br> <input type=button value="Switch All" onClick="switchAll()" class="hexfield1"><br> </form></center>

Simply Cut and Paste Script code
Be sure to properly place script position in HEAD & BODY sections of html

This script has been in the DesignerWiz.com Public Library.