function checkField (elem, value, defaultString){
	if(value == defaultString){
		elem.value='';
	}
}

function restoreField (elem, value, defaultString){
	if(value == ''){
 		elem.value = defaultString;
	}
}

function limitInput (elem, maxlength){
    if (elem.value.length > maxlength){
        elem.value = elem.value.substring(0,maxlength);
    }    
}