Procure no código:

/* Outer-Wrapper----------------------------------------------- */

#outer-wrapper {
width: 900px;
margin:0 auto;
padding:0px;
text-align:left;
font: $bodyfont;
background-color: #bgcolor;
}

#main-wrapper {
margin-left: 5px;
width: 550px;
float: left;
word-wrap: break-word;

/* fix for long text breaking sidebar float in IE */
overflow: hidden; /* fix for long non-text content breaking IE sidebar float */
}

#sidebar-wrapper {
margin-right: 0px;
width: 250px;
float: right;
word-wrap: break-word;
/* fix for long text breaking sidebar float in IE */overflow: hidden;
/* fix for long non-text content breaking IE sidebar float */
}



OBS:
#outer-wrapper é a largura total do blog;
#main-wrapper se refere à coluna do post; e
#sidebar-wrapper se refere a coluna do perfil.