几个div元素在同一行显示的问题

我的问题是如果不设置display:inline;的话就能显示，加上他之后就显示不了了，让我很郁闷

这是HTML

<html>
<title>
<title>Mypage</title>
<script type="text/javascript" src="temp.js"></script>
<link rel="stylesheet" href="temp.css"  type="text/css"/>
<body>
<div id="box">
    <div id="box1"></div>
    <div id="box2"></div>
    <div id="box3"></div>
    <div id="box4"></div>
    <div id="box5"></div>
    <div id="box6"></div>
</div>
</body>
</html>

这是javascript：

window.onload = initAll;

function initAll() {
    var id = document.getElementById("box");
    var littleBoxs = id.childNodes;
    var j = 0;
    for(var i = 0;i <littleBoxs.length;i++){
        if(littleBoxs[i].id != null){
        if(parseInt(littleBoxs[i].id.substr(3,1)) % 2 == 0){
            littleBoxs[i].className = "classRed";
        } else {
            littleBoxs[i].className = "classYellow";
        }
    }
    }
}

这是CSS:

#box {
    height:100px;
    width:600px;
}
.classRed {
    background-color:red;
    display:inline;
    width:100px;
    height:100px;
}
.classYellow {
    background-color:yellow;
    display:inline;
    width:100px;
    height:10px;
}