问题：为什么会如图两个无法起作用的代？
我在html页面应用了如下的css代码，代码的作用好像是取消浮动的。但是现在不起作用，请问为什么？？

CSS代码具体代码是：960-12
/*
960 Grid System ~ Core CSS.
Learn more ~ http://960.gs/

Licensed under GPL and MIT.
*/

/*
Forces backgrounds to span full width,
even if there is horizontal scrolling.
Increase this if your layout is wider.

Note: IE6 works fine without this fix.
*/

body {
min-width: 960px;
}

/* `Containers
----------------------------------------------------------------------------------------------------*/

.container_12 {
margin-left: auto;
margin-right: auto;
width: 960px;
}

/* `Grid >> Global
----------------------------------------------------------------------------------------------------*/

.grid_1,
.grid_2,
.grid_3,
.grid_4,
.grid_5,
.grid_6,
.grid_7,
.grid_8,
.grid_9,
.grid_10,
.grid_11,
.grid_12 {
display: inline;
float: left;
margin-left: 10px;
margin-right: 10px;
}

.push_1, .pull_1,
.push_2, .pull_2,
.push_3, .pull_3,
.push_4, .pull_4,
.push_5, .pull_5,
.push_6, .pull_6,
.push_7, .pull_7,
.push_8, .pull_8,
.push_9, .pull_9,
.push_10, .pull_10,
.push_11, .pull_11 {
position: relative;
}

/* `Grid >> Children (Alpha ~ First, Omega ~ Last)
----------------------------------------------------------------------------------------------------*/

.alpha {
margin-left: 0;
}

.omega {
margin-right: 0;
}

/* `Grid >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .grid_1 {
width: 60px;
}

.container_12 .grid_2 {
width: 140px;
}

.container_12 .grid_3 {
width: 220px;
}

.container_12 .grid_4 {
width: 300px;
}

.container_12 .grid_5 {
width: 380px;
}

.container_12 .grid_6 {
width: 460px;
}

.container_12 .grid_7 {
width: 540px;
}

.container_12 .grid_8 {
width: 620px;
}

.container_12 .grid_9 {
width: 700px;
}

.container_12 .grid_10 {
width: 780px;
}

.container_12 .grid_11 {
width: 860px;
}

.container_12 .grid_12 {
width: 940px;
}

/* `Prefix Extra Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .prefix_1 {
padding-left: 80px;
}

.container_12 .prefix_2 {
padding-left: 160px;
}

.container_12 .prefix_3 {
padding-left: 240px;
}

.container_12 .prefix_4 {
padding-left: 320px;
}

.container_12 .prefix_5 {
padding-left: 400px;
}

.container_12 .prefix_6 {
padding-left: 480px;
}

.container_12 .prefix_7 {
padding-left: 560px;
}

.container_12 .prefix_8 {
padding-left: 640px;
}

.container_12 .prefix_9 {
padding-left: 720px;
}

.container_12 .prefix_10 {
padding-left: 800px;
}

.container_12 .prefix_11 {
padding-left: 880px;
}

/* `Suffix Extra Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .suffix_1 {
padding-right: 80px;
}

.container_12 .suffix_2 {
padding-right: 160px;
}

.container_12 .suffix_3 {
padding-right: 240px;
}

.container_12 .suffix_4 {
padding-right: 320px;
}

.container_12 .suffix_5 {
padding-right: 400px;
}

.container_12 .suffix_6 {
padding-right: 480px;
}

.container_12 .suffix_7 {
padding-right: 560px;
}

.container_12 .suffix_8 {
padding-right: 640px;
}

.container_12 .suffix_9 {
padding-right: 720px;
}

.container_12 .suffix_10 {
padding-right: 800px;
}

.container_12 .suffix_11 {
padding-right: 880px;
}

/* `Push Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .push_1 {
left: 80px;
}

.container_12 .push_2 {
left: 160px;
}

.container_12 .push_3 {
left: 240px;
}

.container_12 .push_4 {
left: 320px;
}

.container_12 .push_5 {
left: 400px;
}

.container_12 .push_6 {
left: 480px;
}

.container_12 .push_7 {
left: 560px;
}

.container_12 .push_8 {
left: 640px;
}

.container_12 .push_9 {
left: 720px;
}

.container_12 .push_10 {
left: 800px;
}

.container_12 .push_11 {
left: 880px;
}

/* `Pull Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .pull_1 {
left: -80px;
}

.container_12 .pull_2 {
left: -160px;
}

.container_12 .pull_3 {
left: -240px;
}

.container_12 .pull_4 {
left: -320px;
}

.container_12 .pull_5 {
left: -400px;
}

.container_12 .pull_6 {
left: -480px;
}

.container_12 .pull_7 {
left: -560px;
}

.container_12 .pull_8 {
left: -640px;
}

.container_12 .pull_9 {
left: -720px;
}

.container_12 .pull_10 {
left: -800px;
}

.container_12 .pull_11 {
left: -880px;
}

/* `Clear Floated Elements
----------------------------------------------------------------------------------------------------*/

/* http://sonspring.com/journal/clearing-floats */

.clear {
clear: both;
display: block;
overflow: hidden;
visibility: hidden;
width: 0;
height: 0;
}

/* http://www.yuiblog.com/blog/2010/09/27/clearfix-reloaded-overflowhidden-demystified */

.clearfix:before,
.clearfix:after {
content: '\0020';
display: block;
overflow: hidden;
visibility: hidden;
width: 0;
height: 0;
}

.clearfix:after {
clear: both;
}

/
The following zoom:1 rule is specifically for IE6 + IE7.
Move to separate stylesheet if invalid CSS is a problem.
/

.clearfix {
zoom: 1;
}