SOURCE

<div id="outer-div">
    <div id="inner-div">100 x 100</div>
    <div id="inner-div">100 x 100</div>
    <div id="inner-div">100 x 100</div>
    <div id="inner-div1">65 x 100</div>
    <div id="inner-div1">65 x 100</div>
    <div id="inner-div">100 x 100</div>
    <div id="inner-div">100 x 100</div>
    400 x  500
</div>

#outer-div{
    height:400px;
    width:500px;
    background-color:red;
}

#inner-div{
    height:100px;
    width:100px;
    background-color:blue;
    float:left;
    margin:10px;
}

#inner-div1{
    height:65px;
    width:100px;
    background-color:pink;
    float:left;
    margin:10px;
}

body{
    background-color:yellow
}