[css layout][05] three percentage columns

1。作者还是全部float向左

 1 #wrapper {
 2   width: 100%;
 3   float: left;
 4 }
 5 #content {
 6   margin-left: 50%;
 7 }
 8 #navigation {
 9   width: 25%;
10   float: left;
11   margin-left: -100%;
12 }
13 #extra {
14   width: 25%;
15   float: left;
16   margin-left: -75%;
17 }
18 #footer {
19   clear: both;
20 }

2.全部float向右

 1 #wrapper {
 2   width: 100%;
 3   float: right;
 4 }
 5 #content {
 6   margin-left: 50%;
 7 }
 8 #navigation {
 9   width: 25%;
10   float: right;
11   margin-right: -25%;
12 }
13 #extra {
14   width: 25%;
15   float: right;
16   margin-right: -50%;
17 }
18 #footer {
19   clear: both;
20 }

3.#wrapper宽度50%全部向右浮动

 1 #wrapper {
 2   width: 50%;
 3   float: right;
 4 }
 5 #navigation {
 6   width: 25%;
 7   float: right;
 8   margin-left: -25%;
 9   position: relative;
10   left: -25%;
11 }
12 #extra {
13   width: 25%;
14   float: right;
15 }
16 #footer {
17   clear: both;
18 }

4.#wrapper宽度50%向左浮动

 1 #wrapper {
 2   width: 50%;
 3   float: left;
 4   margin-right: -50%;
 5   position: relative;
 6   left: 50%;
 7 }
 8 #navigation {
 9   width: 25%;
10   float: left;
11 }
12 #extra {
13   width: 25%;
14   float: left;
15 }
16 #footer {
17   clear: both;
18 }