This javascript cut & paste code snippet allows check boxes to be checked and unchecked based on the selection in another checkbox. If the ALL box is checked off all the other choices go unchecked automatically.  If a choice is selected the ALL box goes unchecked. Useful when constructing search forms, surveys, etc. 

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"> <!-- Original: Scott Waichler --> <!-- Begin function checkChoice(field, i) { if (i == 0) { // "All" checkbox selected. if (field[0].checked == true) { for (i = 1; i < field.length; i++) field[i].checked = false; } } else { // A checkbox other than "Any" selected. if (field[i].checked == true) { field[0].checked = false; } } } // End --> </script>

Insert this code into your BODY section

<center> Please select your favorite class(es): <form name=pickform> <table> <tr> <td><input type=checkbox name=classes value="*" onclick="checkChoice(document.pickform.classes, 0)" checked>All <br> <input type=checkbox name=classes value="science" onclick="checkChoice(document.pickform.classes, 1)">Science <br> <input type=checkbox name=classes value="math" onclick="checkChoice(document.pickform.classes, 2)">Math <br> <input type=checkbox name=classes value="english" onclick="checkChoice(document.pickform.classes, 3)">English <br> <input type=checkbox name=classes value="history" onclick="checkChoice(document.pickform.classes, 4)">Histroy <br> <input type=checkbox name=classes value="other" onclick="checkChoice(document.pickform.classes, 5)">Other </td> </tr></table></form></center>

Example: Please select your favorite classes:

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.