Below I have extended the CHtml helper to have methods that help me locate directories of my assets dynamically. Such assets may include CSS, JavaScript and images.

<?php
class Html extends CHtml
{
	/**
	* Makes the given URL relative to the /image directory
	*/
	public static function imageUrl($url) {
		return Yii::app()->baseUrl.'/images/'.$url;
	}
	/**
	* Makes the given URL relative to the /css directory
	*/
	public static function cssUrl($url) {
		return Yii::app()->baseUrl.'/css/'.$url;
	}
	/**
	* Makes the given URL relative to the /js directory
	*/
	public static function jsUrl($url) {
		return Yii::app()->baseUrl.'/js/'.$url;
	}
}

Methods like the above can be useful for including assets on the client-side. You can use it like in the following:

<?php
echo CHtml::cssFile(Html::cssUrl('reset.css'));
echo CHtml::cssFile(Html::cssUrl('typography.css'));
echo CHtml::cssFile(Html::cssUrl('main.css'));
echo CHtml::cssFile(Html::cssUrl('form.css'));
?>

This is much cleaner and shorter then prefixing the URLs manually. Also, if you ever wish to move the directory of some sort of asset, all you need to do is modify the corresponding method in Html.

You may note that in the above example, Html does not have to extend CHtml. Neither do you have to name the class Html. It's all personal preference.