adds placeholder support to browsers not supporting HTML5 placeholders

jquery.placeholder.js

if ( ! Modernizr.input.placeholder) {
	var phId = 0;
	$('[placeholder]').each(function(){
		var $input = $(this),
		    label = document.createElement('label');
		
		this.id = this.id || 'input-placeholder-' + (++phId);
		label.innerHTML = $input.attr('placeholder');
		label.htmlFor = this.id;
		
		$input.after(label);
		label.style.position = 'absolute';
		label.className = 'placeholder';
		
		var inputHeight = $input.outerHeight(true),
		    labelHeight = $(label).outerHeight(true),
		    paddingLeft = parseInt($input.css('padding-left')) + (parseInt($input.css('margin-left')) || 0) + parseInt($input.css('border-left-width'));

		label.style.top = $input.position().top + Math.floor((inputHeight / 2) - (labelHeight / 2)) + 'px';
		label.style.left = $input.position().left + paddingLeft + 'px';

		var hasText = function() {
			return $input.val() != '';
		};
		
		var showPlaceholder = function() { label.style.display = 'block'; },
		    hidePlaceholder = function() { label.style.display = 'none'; };		
		
		$input.bind('focus blur', function(event){
			if ( ! hasText()) {
				if (event.type === 'focus') hidePlaceholder();
				else showPlaceholder();					
			}
		});
		
		if ( ! hasText()) showPlaceholder();
	});
}