function headerInit()
{
    var searchForm  = $('gsearch');
    var searchInput = $('q');

    searchForm.observe ('submit', function(e) { 
        if(this.searchInput.value == '      Cerca ...') {
            alert('Seleziona il termine di ricerca');
            this.searchInput.focus();
            e.stop();
            return;
        }
        this.action = this.action + this.searchInput.value; 
    });
    searchInput.observe('focus',  function() { if(this.value=='      Cerca ...') {this.value=''; this.removeClassName('qbg')}});
    searchInput.observe('blur',   function() { if(this.value=='') {this.value='      Cerca ...'; this.addClassName('qbg')}});
}

Event.observe(window, 'load', headerInit);