Help with Jquery Opacity

I have a question in javascript.

Why is this not working:

 function scroll_button() { 
        $('div#scrollcase').css('opacity' , 0.3, function() 
        {
     开发者_Python百科       $(this).delay(3500).css('opacity' , 1.0);
        });
    };

Is a loop.

That's not how you use .css(). http://api.jquery.com/css/

Try fadeTo: http://api.jquery.com/fadeTo/

function scroll_button() { 
    $('#scrollcase').fadeTo('slow', 0.3, function() 
    {
        $(this).delay(3500).fadeTo('slow' , 1.0);
    });
};