In the linked preface prayer (But not in the succeeding Sahasranama) non-formal pronunciation is used, since correct representation of pronunciation requires extensive use of diacritic marks. An example: Sanskrit/Hindi has three letters representing S, which are represented here as 's', 'ś', and 'ṣ', as used in the Sanskrit word ṣatkona (= "hexagon"), Viṣnu, Kṛṣṇa and others is actually a retroflex phoneme and has no equivalent in English. Retroflex phonemes are those where the tongue is slightly coiled back in the palate and released along with the phoneme's sound. Also, the 'ṇ' in Viṣṇu and Kṛṣṇa is retroflex. In formal transliteration of Sanskrit alphabet to English, this set-up is denoted by placing dots below the letter 'ṣ'.
Although devotion is considered the most important thing while reciting any prayer or mantra (Unless used for tantric purposes, where the sound's vibration plays the major role), use of the correct pronunciation is believed by devotees to enhance the satisfaction derived from the recital, in the case of both vocal and mental chants.
