.one_half, .one_third, .one_fourth, .two_third, .three_fourth{
    margin-left: 0;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    margin-right: 2%;
    float: left;
    margin-bottom: 20px;
    position: relative
}
.one_half {
    width: 48%
}

.one_third {
    width: 30.6666%
}

.two_third {
    width: 65.3332%
}

.one_fourth {
    width: 22%
}

.three_fourth {
    width: 74%
}

/*
.span12 {
    width: 940px;
}
.span11 {
    width: 860px;
}
.span10 {
    width: 780px;
}
.span9 {
    width: 700px;
}
.span8 {
    width: 620px;
}
.span7 {
    width: 540px;
}
.span6 {
    width: 460px;
}
.span5 {
    width: 380px;
}
.span4 {
    width: 300px;
}
.span3 {
    width: 220px;
}
.span2 {
    width: 140px;
}
.span1 {
    width: 60px;
}*/