checkbox 更改样式

html：

    <div class="wrap">
            <p>1. 勾选</p>
            <input type="checkbox" id="checkbox_a1" class="chk_1" checked /><label for="checkbox_a1"></label>
            <input type="checkbox" id="checkbox_a2" class="chk_1" /><label for="checkbox_a2"></label>
        </div>

css：

.chk_1{
    display: none;
}

/*******STYLE 1*******/
.chk_1 + label {
    background-color: #FFF;
    border: 1px solid #C1CACA;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05), inset 0px -15px 10px -12px rgba(0, 0, 0, 0.05);
    padding: 9px;
    border-radius: 5px;
    display: inline-block;
    position: relative;
    margin-right: 30px;
}
.chk_1 + label:active {
    box-shadow: 0 1px 2px rgba(0,0,0,0.05), inset 0px 1px 3px rgba(0,0,0,0.1);
}

.chk_1:checked + label {
    background-color: #ECF2F7;
    border: 1px solid #92A1AC;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05), inset 0px -15px 10px -12px rgba(0, 0, 0, 0.05), inset 15px 10px -12px rgba(255, 255, 255, 0.1);
    color: #243441;
}

.chk_1:checked + label:after {
    content: '\2714';
    position: absolute;
    top: 0px;
    left: 0px;
    color: #758794;
    width: 100%;
    text-align: center;
    font-size: 1.4em;
    padding: 1px 0 0 0;
    vertical-align: text-top;
}

效果如下：