$(document).ready(function() {
    lastBlock = $("#a1");
    maxWidth = 300;
    minWidth = 100;

    $("ul.accordion li a").hover(function() {
        $(lastBlock).animate({ width: minWidth + "px" }, { queue: false, duration: 400 });
        $(this).animate({ width: maxWidth + "px" }, { queue: false, duration: 400 });
        lastBlock = this;
    }
            );
});