function preventbackspace() {
	//Only allow backspace for entry fields
	if (typeof window.event != 'undefined') {
	        	document.onkeydown = function() {
               	 		if (event.srcElement.tagName.toUpperCase() == 'INPUT' || event.srcElement.tagName.toUpperCase() == 'TEXTAREA'){
				/*allow*/
			}else {
               	         			return (event.keyCode != 8);
               			}
        		}
	} else {
        		document.onkeypress = function(e) {
                		if (e.target.nodeName.toUpperCase() == 'INPUT' || e.target.nodeName.toUpperCase() == 'TEXTAREA') {
				/*allow*/
			}else{
                        			return (e.keyCode != 8);
     			}
		}
	}
}

preventbackspace();