Error: 404 Not Found

Sorry, the requested URL 'http://u.limo/wp-admin/admin-ajax.php?channel_id=social_wechat&action=xh_social_channel&tab=login_redirect_to_authorization_uri&xh_social_channel=eae32193e9&notice_str=1446058185&hash=4ecd366d6078a1bcf59f80711de03c34&redirect_to=https%3A%2F%2Fu.limo%2Ftag%2F%25E4%25B8%2593%25E4%25B8%259A%25E7%2594%25A8%25E9%2580%2594%2F' caused an error:

Not found: '/wp-admin/admin-ajax.php'