function beautify_search_inputs() {
	isSafari = (navigator.userAgent.indexOf("Safari") > 0);
	elements = document.getElementsByClassName('search', null, 'input');
	for (var i = 0; i < elements.length; i++) {
		if (isSafari) { 
			make_search_input(elements[i]);
		}
	}
}

function make_search_input(element) {
	element.type = 'search';
	element.setAttribute('placeholder', element.value);
	element.setAttribute('autosave', 'my.domain.name'); // change this to your own domain name or whatever else 
	element.setAttribute('results', '5');
}

Event.observe(window, 'load', beautify_search_inputs, false);