If anyone of you facing problems to fetch the Magento URL paths of  skin, media, Js or simple base URL of Magento while customization/programming, then following lines should be helpful for you:

Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_JS);
//http://magento.demo/js/

Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_LINK);
//http://magento.demo/index.php/

Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_MEDIA);
//http://magento.demo/media/

Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_SKIN);
//http://magento.demo/skin/

Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_WEB);
//http://magento.demo/