Comparison site operator iSelect has lost its chief executive at the same time as it fields a takeover offer.The company announced yesterday that CEO Alex Stevens had resigned, with immediate effect. Stevens was appointed in March last year.The company has had a fair amount of instability in its senior ranks. After listing on the Australian Securities Exchange in June 2013 it lost a CEO in October of that year.In May last year the chief financial officer David Chalmers resigned.The company's chairman Chris Knoblanche, whose executive roles included managing director corporate and executive banking at Citigroup Australia and New Zealand, took up the role in July. He replaced iSelect co-founder Damien Waller, who moved to the role of non-executive director.The iSelect board has appointed its commercial director Scott Wilson as the new CEO, citing his success in transforming the company's product partner relationships.According to a Fairfax Media report, the "confidential, indicative, non-binding proposal" to acquire iSelect came from a United States private equity group Providence Equity Partners.iSelect said it was in the interests of shareholders to "progress the proposal with a preliminary level of due diligence information and access to senior management."