input取消背景颜色，尤其是边框的背景颜色覆盖了外边包裹的背景颜色时需要。

    <div class="wrapper-search">
            <div class="search">
                <form target="_self" action="?">
                    <input type="text" name="kw" class="txt" value="" title="" placeholder="请输入关键字查询" autocomplete="off"
                        data-keyword="耳机">
                     <input type="submit" class="smt" value="">
                </form>
            </div>
        </div>

 

.wrapper-search{
    width:100%;
    height: 35px;
}

.search {
    position: relative;
    width:10