Page CSS help needed

Where do I change the size of a blog post and its sidebar

Is it one of these, (a three columned themes front page, two column on the post page CSS)

body {
background-color: #ffffff;
padding: 12px;
text-align: center;
font: normal 11px Trebuchet MS;
border-left: 1px solid #eaeaea;
border-right: 1px solid #eaeaea;
letter-spacing: 1px;
color: #5C5C5C;
}
body.home #content {
background: url(images/homebg.gif) repeat-y top left;
min-height:500px;
border: 1px solid #eaeaea;
height:auto !important;
height:500px;
}
body #content {
background: url(images/singlebg.gif) repeat-y;
min-height:500px;
height:auto !important;
height:500px;
}

.left {
width: 260px;
float: left;
padding: 10px;
}
.left .featured .list h3, .left .featured .list .category {
float: none;

}
.post h2 {
font: 20px Trebuchet MS;
padding: 5px 0;
}
.post h2 a {
text-decoration: none;
border-bottom: none;
}
.post h2 a:hover {
background: #ffffff;
}
.post {
padding-bottom: 15px;
background: url(images/stripe.gif) repeat-x bottom;
margin-bottom: 15px;
}
.post hr, .single-main hr {
border-left: none;
border-right: none;
border-top: none;
border-bottom: 2px solid #ffffff;
width: 100px;
}
.post .author {
padding-bottom: 10px;
}
.post .author em {
font-family: Trebuchet MS;
font-style: italic;
}
.focus {
width: 656px;
padding: 10px;
border-bottom: 1px solid #ffffff;
background-color: #fff;
}
.right {
float: left;
width: 678px;
}
.main {
width: 420px;
padding: 10px;
float: left;
}
.main .post h2 {
font-size: 26px;
}
.featured {

}
.featured h2, .sidebar h2, .single-sidebar h2 {
font-size: 13px;
text-transform: uppercase;
font-weight: bold;
margin: 0;
padding: 0;
color: #000;
font-family: Trebuchet MS;
padding-bottom: 10px;
}
.featured h3 a {
font-weight: normal;
font-family: Trebuchet MS;
text-decoration: none;
font-size: 14px;
border-bottom: none;
}
.featured h3 a:hover {
background-color: #ffffff;
}

}
.sidebar {
float: left;
width: 192px;
padding: 10px;
width: 214px;
}
.sidebar a {
border-bottom: none;
}
.sidebar a:hover {
color: #ffffff
}
.sidebar h2 {

}
.sidebar ul {
list-style: none;
padding-bottom: 15px;
}
.sidebar ul li {
padding: 5px 0;
border-bottom: 1px solid #ffffff;
}

}
.single-main {
width: 638px;
padding: 10px;
float: left;
}
.single-main img {
padding: 5px;
background: #ffffff;
border: none;
}
.single-main a img {
border: none;
}
.single-main h2 {
font: normal 26px Trebuchet MS;
color: #000;
}
.single-main .sum {
width: 198px;
float: right;
font-size: 16px;
font-family: Trebuchet MS;
line-height: 22px;
background: #ffffff;
border: 0px solid #ffffff;
padding: 15px;
}
.single-main .author {
padding-bottom: 5px;
}
.single-main .author em {
font-family: Trebuchet MS;
}
.single-main .date {
padding-bottom: 10px;
font-style: italic;
font-family: Trebuchet MS;
}
.single-main h3 {
padding-top: 0px;
font: normal 18px Trebuchet MS;
color: #000;
padding-bottom: 10px;
}
.single-main ol, .single-main ul {
padding: 0px 0px 0px 0px;
line-height: 0px;
}

.post-data {
padding: 0px;
text-align: center;
margin-top: 0px;
text-align: center;
background: url(images/stripe.gif) repeat-x top;
border-bottom: 1px solid #999;
}
.post-data a {
border-bottom: none;
}

.single-sidebar {
padding: 10px;
width: 276px;
float: left;
}
.single-sidebar ul {
list-style: none;
}
.single-sidebar ul li {

}
.single-sidebar ul li ul {
padding-bottom: 45px;
}
.single-sidebar ul li ul li {
padding: 5px 0;
/*background: url(images/stripe.gif) repeat-x bottom;*/
border-bottom: 1px solid #ffffff;
}
.single-sidebar ul li ul li a {

border: none;
}
.single-sidebar ul li ul li a:hover {
background: #ffffff;
}