What are the keys to virality? It's about so much more than just the content. Will people share your stuff? Will they click on it from their news feeds and tweet streams? At seven-month old start-up Upworthy, we've become experts at making stuff that matters go viral. Learn about what we've built and how we've optimized our website to maximize sharing. The lessons here are essential for anyone who wants to spread ideas throughout the modern social web.