HTML+CSS 实现一个简单的登录页面 （背景图片完全适应 不失帧）

 

 

 

 

HTML：

	
		
		
		 
		
	
	

			

			
Login
			

				

					
					Username
				
				

					
					Password
				
				Submit
			
		

		
		 
	

css：

body{
	margin: 0;
	padding: 0;
	font-family: sans-serif;
	background: url(../img/bg.jpg)  no-repeat center 0px;
	background-size: cover;

	

     background-position: center 0; 
     background-repeat: no-repeat;  
     background-attachment: fixed; 
      -webkit-background-size: cover;  
      -o-background-size: cover;  
      -moz-background-size: cover;  
      -ms-background-size: cover;
	
}
.login-box{
	position: absolute;
	top: 50%;
	left: 50%;
	transform: translate(-50%,-50%);
	width: 400px;
	padding:40px;
	background: rgba(0,0,0,.8);
	box-sizing: border-box;
	box-shadow: 0 15px  25px rgba(0,0,0,.5);
	border-radius: 10px;
}
.login-box h2{
	margin: 0 0 30px;
	padding: 0;
	text-align: center;
	color: #fff;
}
.login-box .login-field{
	position: relative;
}
.login-box .login-field  input{
	width: 100%;
	padding: 10px 0;
	font-size: 16px;
	color: #fff;
	margin-bottom: 30px;
	border: none;
	border-bottom: 1px solid #fff;
	outline: none;
	background: transparent;
}
.login-box .login-field  label{
	position: absolute;
	top: 0;
	left: 0;
	letter-spacing: 1px;
	padding: 10px 0;
	font-size: 16px;
	color: #fff;
	pointer-events: none;
	transition: .5s;
}
.login-box .login-field input:focus ~ label,
.login-box .login-field input:valid ~ label{
	top: -23px;
	left: 0;
	color: aqua;
	font-size: 12px;
}
.login-box button{
	background: transparent;
	border: none;
	outline: none;
	color: #fff;
	background: #03a9f4;
	padding: 10px 20px;
	cursor: pointer;
	border-radius: 5px;
}