do you have the template already b/c most blog sites like that can already be downloaded... either look into the CSS file or inside of the index file for the CSS info. CSS is very easy to code i'm sure if your doing the rest you can figure this out.

example:

[CODE] body {
background-image: url(../images/bg.gif);
background-repeat: repeat;
margin-left: 0px;
margin-top: 0px;
margin-right: 0px;
margin-bottom: 0px;
}
div{
margin: 0 ;
padding: 0 ;
}

#container {
padding: 0px;
margin-top: 0px;
margin-bottom: 0px;
margin-left: auto ;
margin-right: auto ;
/* opera does not like 'margin:20px auto' */
text-align:right;
/* part 2 of 2 centering hack */
width: 800; /*ie5win fudge begins */
height: 100%;
background-color: black ;
}
#header{
background-color: black ;
padding: 0px;
margin-bottom: 0px;
}
#headerlogo{
margin-left: auto ;
margin-right: auto ;
}

.BG { background-color: none;
background-image: url(/images/bg.gif);
background-repeat: repeat-x;
background-position: 0px 0px
}


.body {
font-family: Arial, Helvetica, sans-serif;
font-size: 12px;
color: #333333;
line-height: normal;
}
.heading {
font-family: Arial, Helvetica, sans-serif;
font-size: 18px;
font-weight: bold;
color: #666666;
} [/CODE]