It's been in the pipeline for several weeks. But now it looks like a Yahoo purchase of the blogging website Tumblr is happening. Yahoo's board agreed on Sunday to pony up for Instagram-sized pricetag: $1.1 billion. For Tumblr and its 26-year-old founder David Karp, the buy could offer an influx of advertising and business savvy. The website AllThingsD first reported the deal. Kara Swisher, co-founding editor of AllThingsD, says this is a big part of a mission for Yahoo's new chief Marissa Mayer -- a mission to make the aging Internet company cool again.