[css layout][06] three percentage columns

1.#wrapper宽度100%全部float向左

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

2.#wrapper宽度100%全部float向右

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

3.#wrapper宽度50%全部float向右

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

4.#wrapper宽度50%全部float向左

 1 #wrapper {
 2   width: 50%;
 3   float: left;
 4   margin-right: -50%;
 5   position: relative;
 6   left: 50%;
 7 }
 8 #navigation {
 9   float: left;
10   width: 25%;
11   margin-right: -25%;
12   position: relative;
13   left: 25%;
14 }
15 #extra {
16   float: left;
17   width: 25%;
18 }
19 #footer {
20   clear: both; 
21 }