Ayuda con esto, porfi

Hola, a ver si me podeis ayudar con esto, no se porque, y me estoy volviendo loco con esto, pero al agregar comentarios al post llega un momento que la pantalla se me corta, como se puede ver en la imagen:

Save alguien porque puede ser??,he mirado y remirado el css mil veces!!

Gracias

si tienes que decir al cuerpo de la pagina que sea alto automatico (heigth: auto) en el css a ver pon tu css y lo vemos

pues eso lo he intentado mil veces, aqui te pego mi css:

body {
	background: #E9E9E9 url(../img/white-texture.png) repeat;
	font-size: 13px;
	letter-spacing: 0.5px;
	color: #717171;
	font-family: 'Istok Web',arial,serif;
}
html {
	overflow-y:scroll;
}
a {
	text-decoration: none;
     color: #4c62a0;
}
a:hover {
   color: #ef4034;
}
#principal {
	overflow: hidden;
	width: 960px;
	margin: 30px auto 0px auto;
}
#head {
	background: none repeat scroll 0 0 #FFFFFF;
    border-top: 1px solid #c8c6c6;
	border-bottom: 1px solid #c8c6c6;
	height: 66px;
	margin-left: -11px;
    margin-right: -11px;
	margin-top: 14px;
}
#logo {
	float: left;
	height: 50px;
	width: 200px;
	margin-top: 12px;
	margin-left: 20px;
	padding:0px 20px;
}
#logo img{
	-webkit-transition-duration:0.4s;
	-moz-transition-duration:0.4s;
}
#logo img:hover{
	opacity:0.7;
	-webkit-transition-duration:0.4s;
	-moz-transition-duration:0.4s;
}
#buscador {
	float: right;
	width: 285px;
	margin-right: -7px;
	margin-top: 18px;
    width: 329px;
}

#principal {
    background: none repeat scroll 0 0 #F8F7F7;
    border: 1px solid #CDCDCD;
    margin: 34px auto 0;
    overflow: hidden;
    padding: 10px;
    width: 1004px;
	border-radius:10px;

}
body {
    color: #717171;
    font-family: 'Istok Web',arial,serif;
    font-size: 12px;
    letter-spacing: 0.5px;
}
.btnbuscar {
    background-color: #4C62A0;
    background-image: url("../img/btn_mio.png");
    background-position: center center;
    background-repeat: no-repeat;
    border: medium none;
    border-radius: 8px;
    height: 32px;
    margin-right: 5px;
	 margin-left: 10px;
    padding: 8px;
    width: 32px;
	cursor:pointer;
}
.btnbuscar:hover {
	cursor:pointer;
	background-color:#0081f9;
}
#buscar {
	position: relative;
	width: 210px;
	padding: 3px 29px 3px 11px;
	outline: none;
	background: #F7F7F7;
	border: 1px solid #CCC;
	color: #666;
	text-shadow: 1px 1px 1px #FFF;
}
.barrabuscar {
	border: 1px solid #ccc;
	margin-right: -4px;
	margin-top: 3px;
	background: #fff;
	color: #999;
	padding: 0px 5px;
	border-radius: 8px;
	outline: none;
	width: 215px;
	height: 30px;
}
#menu {
	background: #EBE8E8;
	height: 40px;
	border-bottom: 1px solid #c8c6c6;
	margin-bottom: 20px;
	margin-left: -11px;
    margin-right: -11px;
}
#menu a{
	font-weight: bold;
	color: #5c5c5c;
}
#leftt {
	float: left;
	width: 687px;
	height: 300px;
}
#rigthh {
	float: right;
	width: 300px;
}
#section_l {
	padding: 20px;
	background: #FFF;
	border: 1px solid #cdcdcd;
	margin-bottom: 20px;
}
#section_coments {
	padding: 10px;
	background: #fff;
	border: 1px solid #cdcdcd;
	margin-bottom: 5px;
}
#sectio_r {
	padding: 20px;
	background: #FFF;
	border: 1px solid #cdcdcd;
	margin-bottom: 20px;
}
#anuncio {
	/*padding: 20px;*/
	background: #FFF;
	border: 1px solid #cdcdcd;
	margin-bottom: 20px;
}
#tittle_h {
	font-size: 18px;
	color: #535353;
	line-height: 1.5em;
	text-transform: uppercase;
	font-weight: normal;
	text-shadow: 1px 1px 1px #CCC;
}
#tittle_h a {
	color: #535353;
	text-decoration:none;
}
#tittle_h a:hover {
	color: #7da1bc;
}
#post_info {
	font-size: 12px;
	color: #999;
	padding: 7px 0px;
	margin-top: 10px;
	border-top: 1px dashed #c2c2c2;
	border-bottom: 1px dashed #c2c2c2;
}
#item_me {
	padding: 0 22px;
	text-transform:uppercase;
	float:left;
	line-height: 43px;
	height: 40px;
	border-right: 1px solid #C8C6C6;
}
#footer {
    background-color: #EBE8E8;
    border: 1px solid #D9D9D9;
    height: 40px;
    margin: auto auto 14px;
    width: 1025px;
}
#txt_fo {
	text-transform: uppercase;
	padding-top: 14px;
	text-align: center;
	margin: 0px auto;
}
#add468 {
	height: 60px;
	width: 468px;
	float: right;
}

#txt_fo a {
	color: #717171;
	padding:0px 8px;
}
#txt_fo a:hover {
	text-decoration: none;
    color: #7da1bc;
}
#item_op {
	padding: 12px;
	font-weight: bold;
	text-transform:uppercase;
	float: right;
}
.arrow {
	margin: 1px;
}
#left {
	width: 600px;
}

.btn_b {
	background: url(../img/search.png) no-repeat;
	float: right;
	border: none;
	outline: none;
	width: 15px;
	height: 15px;
	cursor: pointer;
	margin-top: -27px;
	margin-right: 5px;
	z-index: 999;
	position: relative;
}
#side_r {
	border-bottom: 1px dashed #CCC;
	padding-bottom: 5px;
	margin-top: 0px!important;
	margin-bottom: 15px;
	color: #535353;
	font-size:14px;
	line-height: 1.5em;
	text-transform: uppercase;
	font-weight: normal;
	text-shadow: 1px 1px 1px #CCC;
}
.in_txt {
    margin-right: 10px;
}
.h_img {
	margin-bottom: -2px;
	margin-right:8px;
}
.txt_side {
	margin-bottom: 5px;
}
.tags_t {
	float: left;
	display: block;
	color: #717171;
	margin-left: 5px;
	margin-bottom: 5px;
	padding: 3px 7px;
	line-height: 1.3em;
	background: #e8e8e8;
}
#notifica_msn {
	text-shadow: 1px 1px 1px #000;
	font-size: 11px;
	padding: 1px 4px;
	position: absolute;
	z-index: 999;
	color:#fff;
	margin-top: -8px;
	margin-left: -15px;
	background-color: #7da1bc;
	font-weight: bold;
	font-family:helvetica,arial,sans-serif;
}
.item_top{
	float:right;
	margin-top:-18px;
	margin-right:10px;
}
#flotante {
    background-color: #FFFFFF;
    border: 3px solid #4c62a0;
    border-radius: 4px;
    left: 604.5px;
    max-height: 682px;
    position: fixed;
    top: 142.75px;
    width: 600px;
    z-index: 10001;
}
#titulo_login{
	background-color: #4c62a0;
    color: #FFFFFF;
    font-size: 12px;
    font-weight: bold;
    padding: 9px 10px;
    text-shadow: 0 1px 0 rgba(0, 0, 0, 0.3);
    text-transform: uppercase;
}
#cerrar_login{
	float:right;
}
#titulo{
	background-color: #4C62A0;
    color: #FFFFFF;
    font-size: 12px;
    font-weight: bold;
    padding: 9px 10px;
	margin-bottom: 20px;
    text-shadow: 0 1px 0 rgba(0, 0, 0, 0.3);
    text-transform: uppercase;
}
#contenido_post{
	padding:8px;
	 margin-bottom: 30px;
	font-size:14px;
	width:595px;
	word-wrap: break-word;/*esto es para que no se salga el texto de sus limites*/
}
#fondo_negro {
    background-color: #000000;
    height: 1581px;
    left: 0;
    opacity: 0.7;
    position: fixed;
    top: 0;
    transition-duration: 0.5s;
    width: 1930px;
    z-index: 10000;
}
#titulo a{
	color: #FFFFFF;
}
#registrados {
    color: #FFFFFF;
    font-size: 12px;
    font-weight: bold;
    text-align: right;
    text-shadow: 0 1px 0 rgba(0, 0, 0, 0.3);
    text-transform: uppercase;
	margin-top:-16px;
}
#registrados a{
	color: #fff;
}
#registrados a:hover{
	color: #d6d6d6;
}
.comentario{
	padding-top:5px;
	border-top: 1px dashed #C2C2C2;
	border-bottom: 1px dashed #C2C2C2;
	font-size: 12px;
}
.coment{
	padding-left:11px;
	padding-top:11px;
	word-wrap: break-word;/*esto es para que no se salga el texto de sus limites*/
	max-width: 501px;
}
.favoritos{
	float:right;
}
#borrar{
	float:right;
}
#borrar a{
	color:#FFF;
}
#borrar a:hover{
	color:#ef4034;
}
.paginacion{
	background-color: #535353;
    border: 1px solid #CDCDCD;
    color: #FFFFFF;
	font-size:10px;
	padding:3px;
    font-family: Tahoma,Verdana,Arial;
	border-radius: 8px;
	text-transform: uppercase;
	cursor: pointer;
}
input {
    background-color: #ececec;
    border: 1px solid #4d4c4c;
    color: #5d5d5d;
    font-family: Tahoma,Verdana,Arial;
}
select {
    background-color: #ececec;
    border: 1px solid #4d4c4c;
    color: #4d4c4c;
    font-family: Tahoma,Verdana,Arial;
}
textarea {
    background-color: #ececec;
    border: 1px solid #4d4c4c;
	font-size:12px;
    color: #4d4c4c;
    font-family: Tahoma,Verdana,Arial;
    height: 75px;
    width: 300px;
}
.boton{
	background-color: #000;
	color:#FFF;
	cursor: pointer;
}
.botar{
	float:right;
	margin-top: -12px;
}
.botos{
	background-color: #717171;
    border-radius: 4px;
    color: #FFFFFF;
    cursor: pointer;
    font-size: 12px;
    font-weight: bold;
    list-style: none outside none;
    margin-right: 1px;
	padding:0px 6px;
}
.botos a:hover{
	background: red;

}
#recordar_password{
	margin-left:10px;
}

#users_online {
    color: #666666;
    float: left;
    padding: 4px 4px 0;
    width: 111px;
    word-wrap: break-word;
}
#user_avatar {
    background: #FFF;
    border: 1px solid #D3D3D3;
    height: 100px;
    margin: 4px;
    padding: 1px;
    width: 100px;
}

#user_nombre {
    font-size: 11px;
    margin: 4px;
    padding: 4px;
    text-align: center;
}

Saves de que puede ser??

Perdon, ya lo he solucionado, a la capa le tenia puesto pincipal en vez de princial


gracias

Que bueno que te diste cuenta :)