CSS自适应宽度圆角按钮
1.背景图片实现 Html代码:

1. a { display: block; float:left; margin-left:5px; height: 37px;line-height: 37px; background: url(btn_bg.png) no-repeat 0px 0px; color: #d84700; text-decoration: none; padding-left:18px; }
2. a span { display:block; background: url(btn_bg.png) no-repeat right 0px; padding-right:20px;}
3. a:hover { background: url(btn_bg.png) no-repeat 0px -37px;}
4. a:hover span{ background: url(btn_bg.png) no-repeat right -37px;}

Html代码:

1. <p>
2. <a href="#"><span>免费注册</span></a>
3. <a href="#"><span>登录</span></a>
4. <a href="#"><span>自适应宽度</span></a>
5. </p>

原理就是做一个足够宽的背景，a和span都用同一张背景图，文字左侧部分显示的是a的背景，文字本身和右侧部分显示的是span的背景，拼接成一个按钮。

2.CSS3 火狐和Chrome实现 Html代码:

1. .button1{
2. -moz-border-radius:5px;
3. -webkit-border-radius:5px;
4. border-radius:5px;
6. -moz-box-shadow:0 1px 0 rgba(0,0,0,0.3);
7. -webkit-box-shadow:0 1px 0 rgba(0,0,0,0.3);
8. box-shadow:0 1px 0 rgba(0,0,0,0.3);
10. background: -moz-linear-gradient(19% 75% 90deg, #E0E0E0, #FAFAFA);
12. background: -webkit-gradient(linear, left top, left bottom, from(#FAFAFA), to(#E0E0E0));
14. color:#4A4A4A;
15. float:left;
16. font-family:arial,helvetica,sans-serif;
17. font-size:17px;
18. font-weight:bold;
19. padding:10px 15px;
20. text-shadow:1px 1px 0 rgba(255, 255, 255, 0.7);
21. }
23. .button1:hover{
24. background: -moz-linear-gradient(19% 75% 90deg,#D6D6D6, #FAFAFA);
25. background: -webkit-gradient(linear, left top, left bottom, from(#FAFAFA), to(#D6D6D6));
26. }

Html代码 :

1. <p><a class="button1">渐变圆角按钮</a></p><br />

效果：
Html代码 :

1. .button7{
2. -moz-border-radius:3px;
3. -webkit-border-radius:3px;
4. border-radius:3px;
6. background: -moz-linear-gradient(19% 75% 90deg,#F0DEB8, #FDF0D1, #fff 100%);
8. background: -webkit-gradient(linear, 0% 0%, 0% 100%, from(#FFFFFF), to(#F0DEB8), color-stop(.3,#FDF0D1));
10. color:#836d4d;
11. float:left;
12. font-family:arial,helvetica,sans-serif;
13. font-size:15px;
14. font-weight:bold;
15. padding:6px 70px;
16. border: 1px solid #d4c198;
17. }
19. .button7:hover{
20. background: -moz-linear-gradient(19% 75% 90deg,#EBD9B4, #F2E6C8, #F5F5F5 100%);
21. background: -webkit-gradient(linear, 0% 0%, 0% 100%, from(#F5F5F5), to(#EBD9B4), color-stop(.3,#F2E6C8));
22. }
23. <a class="button7"></a>