[Rise]

<form name="form1">
	<input type="text" name="url" value="Введите адрес сайта ..." size="50" />
	<button type="submit">Go</button>
</form>
<iframe height="50" width="50"></iframe>
<iframe height="60" width="60"></iframe>
<iframe height="70" width="70"></iframe>
<iframe height="80" width="80"></iframe>

<script>
document.form1.url.onfocus = function() {
	if (this.value == this.defaultValue) this.value = '';
}
document.form1.url.onblur = function() {
	if (this.value == '') this.value = this.defaultValue;
}
document.form1.onsubmit = function() {
	var url = this.url.value;
	var validurl = 'http://www.';
	validurl += url.replace(/^(https?:\/\/(www\.)?|\/\/(www\.)?|www\.)/i, '');
	var iframe = document.getElementsByTagName('iframe');
	for (var key in iframe) {
		iframe[key].src = validurl;
	}
	return false;
}
</script>