Irvine-based online advertising firm WebVisible has shut down, according to a report Wednesday. Former WebVisible employees had been telling socalTECH over the last few months that the firm was looking for a buyer. The company has not yet confirmed the shutdown, however, founder and CEO Kristen Mangers had left the firm in January in 2011. WebVisible had raised over $37M in venture capital, from such investors as Adams Street Partners, Redpoint Ventures, and Sutter Hill Ventures.