div{
    white-space:nowrap;
}
#da{
    position:relative;
	top:0px;
	}
	
#nav1{
    position:absolute;
	top: 500px;
	left: 940px;
	z-index:13;
	}
#nav1 a:link { 
color:#99FF99;
text-decoration:none;
}
#nav1 a:visited { 
color:#00FF00; 
text-decoration:none; 
} 
#nav1 a:hover{
color:#FFFF00;
text-decoration:blink;
font-weight:bold; 
}

#nav2{
     position:fixed; 
	 top: 350px;
	 left:660px;
	 z-index:12;
}
#nav2 a:link { 
color:#FFFF00;
text-decoration:none;
}

#nav2 a:visited { 
color:#FFFF00;
text-decoration:none; 
}

#nav2 a:hover{
color:#FF0000;
text-decoration:blink;
font-weight:bold;
}

#nav3{
    position:fixed;    
    left:500px;  
    top:500px;
	z-index:11;
}

#nav3 a:link { 
color:#FFFF00;
text-decoration:none;
}
#nav3 a:visited { 
color:#FFFF00;
text-decoration:none;
}
#nav3 a:hover{
color:#FF0000;
text-decoration:blink;
font-weight:bold;
}

@media only screen and (max-width: 640px) {
  /*这里书写手机端的css代码，手机端的css代码是在pc端的代码基础上书写，类似于补充*/
#nav1{
    position: fixed; 
	top:300px;
	left: 150px;
	z-index:13;
	}
#nav1 a:link { 
color:#99FF99;
text-decoration:none;
}
#nav1 a:visited { 
color:#00FF00; 
text-decoration:none; 
} 
#nav1 a:hover{
color:#FFFF00;
text-decoration:blink;
font-weight:bold; 
}

#nav2{
     position:fixed; 
	 top: 340px;
	 left:280px;
	 z-index:12;
}
#nav2 a:link { 
color:#FFFF00;
text-decoration:none;
}

#nav2 a:visited { 
color:#FFFF00;
text-decoration:none; 
}

#nav2 a:hover{
color:#FF0000;
text-decoration:blink;
font-weight:bold;
}

#nav3{
    position:fixed;    
    left:200px;  
    top:500px;
	z-index:11;
}

#nav3 a:link { 
color:#FFFF00;
text-decoration:none;
}
#nav3 a:visited { 
color:#FFFF00;
text-decoration:none;
}
#nav3 a:hover{
color:#FF0000;
text-decoration:blink;
font-weight:bold;
}
}