[CSS] 自相应式菜单

  <nav class="nav">
        <ul>
            <li class="current"><a href="#">Portfolio</a></li>
            <li><a href="#">Illustration</a></li>
            <li><a href="#">Web Design</a></li>
            <li><a href="#">Print Media</a></li>
            <li><a href="#">Graphic Design</a></li>
        </ul>
    </nav>

 .nav {
            position: relative;
            margin: 20px 0;
        }

            .nav ul {
                margin: 0;
                padding: 0;
            }

                .nav ul li {
                    margin: 0 5px 10px 0;
                    padding: 0;
                    list-style: none;
                    float: left;
                }

            .nav a {
                padding: 3px 12px;
                text-decoration: none;
                color: #999;
                line-height: 100%;
            }

                .nav a:hover {
                    color: #000;
                }

            .nav .current a {
                background: #999;
                color: #fff;
                border-radius: 5px;
            }
            /* right nav */
            .nav.right ul {
                text-align: right;
            }

            /* center nav */
            .nav.center ul {
                text-align: center;
            }

        @media (max-width: 600px) {
            .nav {
                position: relative;
                min-height: 30px;
            }

                .nav ul {
                    width: 180px;
                    padding: 5px 0;
                    position: absolute;
                    top: 0;
                    left: 0;
                    border: solid 1px #aaa;
                    background: #fff url(images/icon-menu.png) no-repeat 10px 11px;
                    border-radius: 5px;
                    box-shadow: 0 1px 2px rgba(0,0,0,.3);
                }

                .nav li {
                    display: none; /* hide all <li> items */
                    margin: 0;
                }

                .nav .current {
                    display: block; /* show only current <li> item */
                }

                .nav a {
                    display: block;
                    padding: 5px 5px 5px 32px;
                    text-align: left;
                }

                .nav .current a {
                    background: none;
                    color: #666;
                }

                /* on nav hover */
                .nav ul:hover {
                    background-image: none;
                }

                    .nav ul:hover li {
                        display: block;
                        margin: 0 0 5px;
                    }

                    .nav ul:hover .current {
                        background: url(images/icon-check.png) no-repeat 10px 7px;
                    }

                /* right nav */
                .nav.right ul {
                    left: auto;
                    right: 0;
                }

                /* center nav */
                .nav.center ul {
                    left: 50%;
                    margin-left: -90px;
                }
        }