A quick solution.
Instead of a reset button have a standard button and set its onclick handler to "selectiveReset(this.form)", assuming the element whose value you want to preserve is named "txtSpecial":
Code:
function selectiveReset(frm)
{
var oInput = frm["txtSpecial"];
var sValue = oInput.value;
frm.reset();
oInput.value = sValue;
}
--
Joe