CSS ne cesse de fonctionner

*
{
padding:0;
margin:0;
}
body
{
  background-color:#000;
  font-family:arial;
  background: url(noir.jpeg);
  
}
#content
{
width:960px;
background-color:#FFF;
margin:50px auto;
text-align:center;
border-radius:10px;
-webkit-border-radius:10px;
-moz-border-radius:10px;
position:relative;
}
#content h1,h3
{
  text-decoration:underline;
  padding-bottom:20px;
}
#content form label
{
  display:block;
  float:left;
  width:200px;
  position:absolute;
  left:100px;
}
#content form input,textarea
{
border:1px solid #000;
border-radius:5px;
-webkit-border-radius:5px;
-moz-border-radius:5px;
width:200px;
margin:5px;
}
#content form input[type=submit]
{
  width:100px;
  background-color:#000;
  color:#FFF;
  cursor:pointer;
}
#content .error
{
  color:red;
  border-radius:5px;
 -webkit-border-radius:5px;
 -moz-border-radius:5px;
  margin:2px auto;
  width:300px;
  background-color:#CCC;
  text-align:center;
}
  #content .success
{
  color:green;
  border-radius:5px;
 -webkit-border-radius:5px;
 -moz-border-radius:5px;
  margin:2px auto;
  width:300px;
  background-color:#CCC;
  text-align:center;
 
}
#content .header
{
text-align:right;
margin-right:5px;
}
#content  .menu
{
height:35px;
line-height:1.5em;
background-color:#cdd3fd;
border:1px solid #000;
}
#content .menu ul li
{
   float:left;
   list-style:none;
   line-height:36px;
   border-left:1px solid #000;
}
#content .menu ul li a
{
   color:#000;
   text-decoration:none;
   padding:25px;


}
#content .menu li.nbr
{
   color:green;
   padding-left:20px;
}

#content .info {
    text-align:left;
    padding:20px;
}
 
.info strong {
    text-decoration:underline;
}
 
.info em {
    color:blue;
}

#content img {

  border:1px solid #000;
}
#content .info p a {

  color:red;
  padding-left:30px;
}

.center
{
margin: auto;
width: 100%;

}

.ibi_invitations
{
 margin: auto;
 background-color: #FF0000;
 border: 1px solid #000;
 color: #FFF;
 position: absolute;
 border-radius: 100%;
 -moz-border-radius: 100%;
 -webkit-border-radius: 100%;
 width: 20px;
 height: 20px;
 left: 680px;
 top: 75px;
 text-align: center;
 line-height: 20px;
 color: black;
}

.conversation, .messages
{
  width:600px;
  background-color:#333;
  margin:0 auto;
  border-radius:10px;
  -moz-border-radius:10px;
  -webkit-border-radius:10px;
}
.conversation a
{
  color:pink;
}
.conversation p a
{
  color:#FFF;
}
.messages a 
{
 color: pink;
}
.messages p
{
 color: white;
}
.messages p em
{
 color: lightgreen;
}

.ibi_messages 
{ 
 margin: auto;
 background-color: #FF0000;
 border: 1px solid #000;
 color: #FFF;
}

Je souhaite changer de background, et malgré mes modifs ça ne marche pas