html - Scrolling only content div, others should be fixed

Question

I have three divs. I need header and left_side divs to be fixed and content div to scroll. I've been searching for solution and found something with overflow and position. But I can not use it corectly. How can I do this? I will be thankfull for every kind of answer.

body {   
    width: 100%;
    height: auto;
    padding: 0;
    margin: 0px auto;
    font-family: Calibri, Georgia, Ubuntu-C;  
    font-size: 16px;
    margin-bottom: 20PX
}

#header{
    width: 100%;
    height: 139px;
    background-image: url('images/Header_grey.gif');   
}


#left_side {
    width: 210px;
    height: 700px;
    background-image: url('images/Left_side.gif');
    background-repeat:repeat-y;
    overflow:hidden; 
    position:absolute;
    font-size: 16px;
}

#content {
     height: auto;
     padding: 20px;
     margin-left: 230px;
     margin-right: 20px;
    padding-bottom: 30px
}

<div id="header">
</div>

<div id="left_side">    
</div>

<div id="content">
</div>

Answer 1

overflow: auto; adds the scroll when need

#header{
    width: 100%;
    height: 139px;
    background-image: url('images/Header_grey.gif');   
    overflow: hidden;  /* code added to prevent scroll */
}
    
    
#left_side{
    width: 210px;
    height: 700px;
    background-image: url('images/Left_side.gif');
    background-repeat:repeat-y;
    overflow:hidden;  /* code added to prevent scroll */
    position:absolute;
    font-size: 16px;
}
#content{
    height: auto;
    padding: 20px;
    margin-left: 230px;
    margin-right: 20px;
    padding-bottom: 30px;
    overflow: auto;  /* code added */
}