正确使用IMG

如果您打算使用IMG 人们打印您的页面，您希望在默认情况下包含图像。 -JayTee 当图像具有重要的语义含义时，例如警告图标，使用IMG(带有alt文本)。这确保了图像的含义可以在所有用户代理(包括屏幕阅读器)中传达。

IMG的实用用途

Use IMG plus alt attribute if the image is part of the content such as a logo or diagram or person (real person, not stock photo people). —sanchothefat Use IMG if you rely on browser scaling to render an image in proportion to text size. Use IMG for multiple overlay images in IE6. Use IMG with a z-index in order to stretch a background image to fill its entire window.Note, this is no longer true with CSS3 background-size; see #6 below. Using img instead of background-image can dramatically improve performance of animations over a background.

何时使用CSS背景图像

Use CSS background images if the image is not part of the content. —sanchothefat Use CSS background images when doing image-replacement of text eg. paragraphs/headers. —sanchothefat Use background-image if you intend to have people print your page and you do not want the image to be included by default. —JayTee Use background-image if you need to improve download times, as with CSS sprites. Use background-image if you need for only a portion of the image to be visible, as with CSS sprites. Use background-image with background-size:cover in order to stretch a background image to fill its entire window.

如果您希望图像是流动的并可缩放到不同的屏幕尺寸，则可以使用IMG标记。对我来说，这些图片主要是内容的一部分。对于大多数不属于内容的元素，我使用CSS精灵来保持最小的下载大小，除非我真的想要动画图标等。

此外，我有一个画廊部分，有不一致的图片大小，所以即使这些图像显然被认为是内容，我使用背景图像和中心它们在divs设置大小。这类似于facebook在他们的相册里做的事情。

只是在工作中抛出一个扳手-我的意见是，你不应该使用img标签。HTML意味着内容，而不是视觉风格。你页面上的所有图像都应该来自CSS，让你的HTML代码纯粹。(即使它确实需要更长的时间来构建)

我想再补充两个论点:

An img tag is good if you need to resize the image. E.g. if the original image is 100px by 100 px, and you want it to be 80px by 80px, you can set the CSS width and height of the img tag. I don't know of any good way to do this using background-image. EDIT: This can now also be done with a background-image, using the background-size CSS3 attribute. Using background-image is good when you need to dynamically switch between sprites. E.g. if you have a button image, and you want a separate image displayed when the cursor is hovering over the element, you can use a background image containing both the normal and hover sprites, and dynamically change the background-position.

当我想让它们100%可拉伸时，我使用image而不是background-image，大多数浏览器都支持。