I want this script to work when page load and also when resize

Question

The site is responsive

$(window).bind('resize', function() {
    $('#drop_ul').css('width', $('#container').width());
    $('#drop_ul').css('left', $('#container').css('margin-left'));
});

$(document).ready(function(){
    $('#drop_ul').css('width', $('#container').width());
    $('#drop_ul').css('left', $('#container').css('margin-left'));
});

Answer 1

You can extract the logic in to its own function which you can then call under both events. Try this:

function updateUI() {
    $('#drop_ul').css({
        'width': $('#container').width(),
        'left': $('#container').css('margin-left')
    });
}

$(document).ready(function() {
    updateUI(); // on load
    $(window).on('resize', updateUI); // on window resize
});

Note that I unified the css() calls, and used the preferred on instead of bind .

Also, if the site is responsive is would be best to use CSS media queries for this.