#heart{width:100%}

#post{
width:50px;
float:left;
text-align:left;
padding:5px;
margin:1px;
font-family:Verdana, Geneva, sans-serif;
font-size:12px;
color:#605f5f;
background-color:#f7f6f6;
}

#listapost{margin:0 auto;}

<div id="heart">
     <div id="listapost">
       <div id="post">stuff</div>
       <div id="post">stuff</div>
       <div id="post">stuff</div>
       ....
     </div>
</div>