Edit in JSFiddle

#content {
    border:1px solid #7e7e7e; 
    height:150px;
    min-width:100px;
}
#list div {
    border:1px solid #7e7e7e;   
    background:#cbe4fa;       
    margin:0.3em;
    text-align:center;
    width:80px;
    /* 最主要就下面這行 */    
    float:left;
}

<div id="content">
    <div id="list">
        <div>1</div>
        <div>2</div>
        <div>3</div>
        <div>4</div>        
        
    </div>
        

</div>

$( "#content" ).resizable();