jQuery is Showing No Effect

I’m trying to get jQuery on my local XAMPP installation to work with WordPress 3.1, but it seems it has no effect.

This is what I do, I add this following code into the header shortly before the </head> tag:

<?php
	wp_enqueue_script( 'jquery' );
	wp_enqueue_script('custom-jquery', get_bloginfo('stylesheet_directory') . '/js/custom-jquery.js', array('jquery'), '20110417' );

	if ( is_singular() ) wp_enqueue_script('comment-reply');

	wp_head(); 	?>

And then I have this in the custom-jquery.js file:

jQuery(function(){ /*<- shortcut for document ready*/
jQuery(".post").css("background-color", "#ff6600");
});//end docReady

But nothing is happening, the background color does not change. I was able to get jQuery to work on a normal HMTL document on my localhost, but I’m not able to get it to work with WordPress.

Any ideas what the cause for this problem is?