Onfocus and Onblur input field

<input id="search_field" type="text" name="s" value="Search this blog" onfocus="if (this.value == 'Search this blog') {this.value = ''; document.getElementById(this.id).style.color='#666666';}" onblur="if (this.value == '') {document.getElementById(this.id).style.color='#cccccc'; this.value = 'Search this blog'; }" />