http://jigsaw.w3.org/css-validator

perchè mi restituisce un errore simile:

URI : file://localhost/kor.css


Line : 34 Level : 1 You have no color with your background-color : .top


Line : 44 Level : 1 You have no color with your background-color : #titolo


Line : 63 Level : 1 You have no color with your background-color : .welcome


Line : 87 Level : 1 You have no color with your background-color : .ilsito


Line : 101 Level : 1 You have no color with your background-color : #destra


Line : 131 Level : 1 You have no color with your background-color : #basso


Line : 134 Level : 1 You have no background-color with your color : .basso

nel mio css ho questo codice (solo un parte)

.top { background-color: #222; height:70px; }

#titolo { background-color: #333; border-bottom: 2px solid #222;
margin:0px 0px 5px 0px;}

.welcome { margin:0px; padding:0px; border: 1px solid #000;
background-color: #333;
background-image: url(../img/bg_striscie.gif) ;
background-repeat: repeat-y;
background-position: right; }

.ilsito { margin:0px; padding: 2px 10px; background-color: #222;}

#destra { position:relative; float:right; margin:0px; padding:0px;
background-color: #333; border: 1px solid #000; width:160px; }

#basso { background-color: #111; border-bottom: 1px dotted #999;
margin:5px 0px 0px 0px; padding:0px;}

.basso { font: bold 10px Verdana , Helvetica , Sans-serif; color:#F30 ;
margin-left: 10px; line-height:18px; }

è solo la parte con gli errori , dove sbaglio