$('.default-value').each(function() {
    var default_value = this.value;
    $(this).focus(function() {
        if(this.value == default_value) {
	    this.value = '';
	    $(this).css('color', '#000');
        }
    });
    $(this).blur(function() {
        if(this.value == '') {
            $(this).css('color', '#999');
	    this.value = default_value;
	}
    });
});

If your HTML form fields have a 'watermark' default value, it will be removed when the field is focussed and replaced if focus is lost (and the user has left the field blank).

To use give your form field a class of 'default-value'

Remove/restore a form field's default value on focus/blur

form

jQuery