Question

any one can explain me how this filter(‘:first’).click() working?

$(function() {
    var tabContainers = $('div.tabs > div');
    tabContainers.hide().filter(':first').show();
    $('div.tabs ul.tabNavigation a').click(function() {
        tabContainers.hide();
        tabContainers.filter(this.hash).show();
        $('div.tabs ul.tabNavigation a').removeClass('selected');
        $(this).addClass('selected');
        return false;
    }).filter(':first').click();
});

Answer 1

It’s like this:

when you click on div.tabs ul.tabNavigation a . the click function defined just after the
$('div.tabs ul.tabNavigation a') in your code will be executed. and moreover since you added another click i.e filter(':first').click(); , the click function executed earlier, will be executed again for
first ul a (i.e first link in the list)