CSS dynamic width

Question

So I have a "post" system and I want the box to get larger as more posts come in. Here's what I see

This is what happens as I add another post

I just want it to keep adding height as more posts get posted. Here's what I'm currently using

<div class="comment">
        <div class="comment_cont">
        <div class="icons">
        <i class="fa fa-heart"></i>
        <i class="fa fa-comment"></i>
        </div>
        <h1 class="message">@alex likes cats</h1>
        <p class="time">4 minutes ago</p>       
        </div>  
            <div class="comment_cont">
        <div class="icons">
        <i class="fa fa-heart"></i>
        <i class="fa fa-comment"></i>
        </div>
        <h1 class="message">@alex likes cats</h1>
        <p class="time">4 minutes ago</p>       
        </div>  

    </div>

And my CSS

*{
    padding: 0;
    margin: 0 auto;
}
html{
    height: 100%;
}
body{
    background: #F6F5F6;
    height: 100%;
}


.follow{
        font-size: 23px;
        font-family: 'Avenir Next';
        font-weight: 500;   
        display: inline-block;  
        margin-right: -62%
}
.likes{
    padding-left: 20px;
}

.message{
    font-family: 'Avenir Next';
    font-weight: 400;
    padding-left: 35px;
    line-height: 70px;
}

.post{
    width: 100%;
    height: 100px;
    border-bottom: 1px solid #ccc;
}
.fa-heart{  
    transition: 0.5s;
    margin-top: 60px;
    color: #000;
    font-size: 24px;
    float: right;
    margin-right: 30px;
    cursor: pointer;
}
.fa-heart:hover{
    transition: 0.5s;   
    margin-top: 60px;
    color: #FF6699;
    font-size: 24px;
    float: right;
    margin-right: 30px;
    cursor: pointer;
}
.fa-comment{    
    transition: 0.5s;
    margin-top: 60px;
    color: #000;
    font-size: 24px;
    float: right;
    margin-right: 18px;
    cursor: pointer;
}
.fa-comment:hover{
    transition: 0.5s;   
    margin-top: 60px;
    color: #FF6699;
    font-size: 24px;
    float: right;
    margin-right: 18px;
    cursor: pointer;
}
.icons{
    float: right;
    margin-right: 0px;
}
.time{
    font-family: 'Avenir Next';
    padding-left: 40px;
    color: #929292;
    padding-bottom: 20px;
    border-bottom: 1px solid #ccc;
}

.comment{
    border-radius: 15px;
    margin-top: 150px;
    width: 750px;
    height: 200px;
    background: #fff;
    border: 1px solid #ccc;
}   

Here's a demo

Answer 1

Just an add on to Issam's post. You don't really need to specify a height. Since you'll dynamically adding it with the comments. So

.comment{
    border-radius: 15px;
    margin-top: 150px;
    width: 750px;
    background: #fff;
    border: 1px solid #ccc;
}

Would work fine as well

Answer 2

Just use min-height instead of height

.comment{
    border-radius: 15px;
    margin-top: 150px;
    width: 750px;
    min-height: 200px;
    background: #fff;
    border: 1px solid #ccc;
}

http://jsfiddle.net/pFN4X/