<code lang="javascript">// zeroField helper function
function zeroField(el, decimal) {
	var def_val;	
	if(!el) {
		return false;
	} else {
		if(decimal == true) {
			def_val = '0.00';
		} else {
			def_val = '0';
		}
		
		if(el.value == "" || el.value == null) {el.value = def_val;}
		el.onfocus = function() { if (this.value==def_val) this.value = ''; };
		el.onblur  = function() { if (this.value=='') this.value = def_val; };
	}
}

// Demonstration code
function init() {
	var myTextfield = document.getElementById('myTextfield');
	zeroField(myTextfield); // Will set the value of myTextfield to '0'
}

function init() {
	var myTextfield = document.getElementById('myTextfield');
	zeroField(myTextfield, true); // Will set the value of myTextfield to '0.00'
}

window.onload = init;</code>