function trim( str, charlist ) {  
    charlist = !charlist ? ' \s\xA0' : charlist.replace(/([\[\]\(\)\.\?\/\*\{\}\+\$\^\:])/g, '\$1');  
    var re = new RegExp('^[' + charlist + ']+|[' + charlist + ']+$', 'g');  
    return str.replace(re, '');  
}  

function checkSearchCriteria() {
	checkElement = document.getElementById("strKeywords"); 
	element_value = trim( checkElement.value );
	var phrase = "Inserisci un alimento o una bevanda per calcolare le calorie";
	if (element_value != "" && element_value != phrase) {
		return true;
	}
	checkElement.value = phrase;
	return false;
}