Css - 用徽标图像替换 H1 文本:SEO 和可访问性的最佳方法？

似乎有几种不同的技术，所以我希望在这个问题上得到一个"明确的"答案……

在网站上，创建链接到主页的徽标是常见的做法.我也想做同样的事情，同时对搜索引擎、屏幕阅读器、IE 6+和禁用CSS和/或图像的浏览器进行最佳优化.

Example One:不使用h1标签.对搜索引擎优化没那么好，对吧？

<div id="logo">
    <a href="">
        <img src="logo.png" alt="Stack Overflow" />
    </a>
</div>

Example Two:人在某处找到了这个.CSS看起来有点不太好用.

<h1 id="logo">
    <a href="">Stack Overflow</a>
</h1>

/* css */
#logo {
    padding: 70px 0 0 0;
    overflow: hidden;
    background-image: url("logo.png");
    background-repeat: no-repeat;
    height: 0px !important;
    height /**/:70px;
}

Example Three:个相同的HTML，不同的方法使用文本缩进.这就是图像替换的"Phark"方法.

<h1 id="logo">
    <a href="">Stack Overflow</a>
</h1>

/* css */
#logo {
    background: transparent url("logo.png") no-repeat scroll 0% 0%;
    width: 250px;
    height: 70px;
    text-indent: -3333px;
    border: 0;
    margin: 0;
}

#logo a {
    display: block;
    width: 280px; /* larger than actual image? */
    height: 120px;
    text-decoration: none;
    border: 0;
}

Example Four:The Leahy-Langridge-Jefferies method.在关闭图像和/或CSS时显示.

<h1 id="logo" class="logo">
    <a href="">Stack Overflow</a>
</h1>

/* css */
h1.logo {
    margin-top: 15px; /* for this particular site, set this as you like */
    position: relative; /* allows child element to be placed positioned wrt this one */
    overflow:hidden; /* don’t let content leak beyond the header - not needed as height of anchor will cover whole header */
    padding: 0; /* needed to counter the reset/default styles */
}

h1.logo a {
    position: absolute; /* defaults to top:0, left:0 and so these can be left out */
    height: 0; /* hiding text, prevent it peaking out */
    width: 100%; /* 686px; fill the parent element */
    background-position: left top;
    background-repeat: no-repeat;
}

h1#logo {
    height: 60px; /* height of replacement image */
}

h1#logo a {
    padding-top: 60px; /* height of the replacement image */
    background-image: url("logo.png"); /* the replacement image */
}

对于这种事情，什么方法是最好的呢？请在您的答案中提供html和css.