Garry Tan, the co-founder of Posterous, is stepping down from the blog company to join Y Combinator as the designer-in-residence. “Though my day-to-day may change, my faith in the team and the product is unchanged and unwavering. Posterous is in good hands and on the right track to fulfilling its potential. I am proud of what we’ve built together and look forward to the future,” said Tan in a blog post. He will continue his involvement in Posterous as an adviser.

Posterous is a blog publishing service that has raised $4.4 million from Redpoint Ventures. Satish Dharmaraj, Partner at Redpoint is also on the company’s board of directors. Posterous was founded by Sachin Agarwal, Garry Tan, and Brett Gibson in 2008 as a Y-Combinator company. Posterous profiles have no restrictions on usage and custom CSS can be added to blogs. Posterous has about 12 million unique visitors and 25 million page views per month. [TechCrunch]