Shiva marriage with Sati was opposed by King Daksha. Followed by a holy sacrifice (yagnya) King Daksha ignored Lord Shiva and the insult was unbearable by Sati. In a gesture of extreme anger Sati jumped into the sacrificial fire. Upon the death of his beloved, Shiva unleashed his fury and performed the Tandava. Gods then feared the end of the universe and revived Sati as a new avatar of Maa Parvati. Shiva- Parvati union is celebrated on Maha Shivratri
http://en.wikipedia.org/wiki/Maha_Shivaratri#Pralaya_.28the_Deluge.29.
http://blog.prabhubhakti.com/2011/05/the-importance-of-mahashivaratri/
http://kshetrapuranas.wordpress.com/2009/07/03/cupids-sad-tale-thirukurukkai/
