一，效果图。
二，代码。
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>CSS Positioning</title> <style> p.pos_fixed { position: fixed; top: 30px; right: 5px; } h2.pos_left { position: relative; left: -20px; } h2.pos_right { position: relative; left: 20px; } h2.pos_top { position: relative; top: -50px; } h2.absolute { position: absolute; left: 100px; top: 150px; } img { position: absolute; left: 0px; top: 0px; z-index: -1; } </style> </head> <body> <p class="pos_fixed">Some more text</p> <p><b>Note:</b> IE7 and IE8 supports the fixed value only if a !DOCTYPE is specified.</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <p>Some text</p> <h2>This is a heading with no position</h2> <h2 class="pos_left">This heading is moved left according to its normal position</h2> <h2 class="pos_right">This heading is moved right according to its normal position</h2> <p>Relative positioning moves an element RELATIVE to its original position.</p> <p>The style "left:-20px" subtracts 20 pixels from the element's original left position.</p> <p>The style "left:20px" adds 20 pixels to the element's original left position.</p> <h2>This is a heading with no position</h2> <h2 class="pos_top">This heading is moved upwards according to its normal position</h2> <p><b>Note:</b> Even if the content of the relatively positioned element is moved, the reserved space for the element is still preserved in the normal flow.</p> <h2 class="absolute">This is a heading with an absolute position</h2> <p>With absolute positioning, an element can be placed anywhere on a page. The heading below is placed 100px from the left of the page and 150px from the top of the page.</p> <h1>This is a heading</h1> <img src="w3css.gif" width="100" height="140" /> <p>因为图像元素设置了 z-index 属性值为 -1, 所以它会显示在文字之后。</p> </body> </html>
参考资料：《菜鸟教程》