Calling Javascript from Controller in MVC

I'm guessing you are using jQuery AJAX, based on the jQuery tag on the question. In that case, you need to change your "checked" attribute in one of the callback functions to ensure that it fires after the AJAX is complete. You should use the success or complete callback function, depending on what you want.

$.ajax({
    url: whatever,
    data: { whatever: whatever },
    type: 'GET',
    success: function (data, status, jqXHR) {
        $(".selsts").attr('checked', false);
    }
});

The success callback function will fire only if there are no errors. The complete callback function will always fire, after the success callback, if there was one.