Html
    Css
    Js

    
                        
body {
	background-color:#FAFAFA;
}
.top-banner {
	background:#555;
}
input[type="text"] {
	-webkit-box-sizing:border-box;
	-moz-box-sizing:border-box;
	box-sizing:border-box;
	width:100%;
	height:-webkit-calc(3em + 2px);
	height:calc(3em + 2px);
	margin:0 0 1em;
	padding:1em;
	border:1px solid #cccccc;
	border-radius:1.5em;
	background:#fff;
	resize:none;
	outline:none;
}
input[type="text"][required]:focus {
	border-color:#00bafa;
}
input[type="text"][required]:focus + label[placeholder]:before {
	color:#00bafa;
}
input[type="text"][required]:focus + label[placeholder]:before,input[type="text"][required]:valid + label[placeholder]:before {
	-webkit-transition-duration:.2s;
	transition-duration:.2s;
	-webkit-transform:translate(0,-1.5em) scale(0.9,0.9);
	-ms-transform:translate(0,-1.5em) scale(0.9,0.9);
	transform:translate(0,-1.5em) scale(0.9,0.9);
}
input[type="text"][required]:invalid + label[placeholder][alt]:before {
	content:attr(alt);
}
input[type="text"][required] + label[placeholder] {
	display:block;
	pointer-events:none;
	line-height:2.3em;
	margin-top:-webkit-calc(-3em - 2px);
	margin-top:calc(-3em - 2px);
	margin-bottom:-webkit-calc((3em - 1em) + 2px);
	margin-bottom:calc((3em - 1em) + 2px);
}
input[type="text"][required] + label[placeholder]:before {
	content:attr(placeholder);
	display:inline-block;
	margin:0 -webkit-calc(1em + 2px);
	margin:0 calc(1em + 2px);
	padding:0 2px;
	color:#898989;
	white-space:nowrap;
	-webkit-transition:0.3s ease-in-out;
	transition:0.3s ease-in-out;
	background-image:-webkit-gradient(linear,left top,left bottom,from(#ffffff),to(#ffffff));
	background-image:-webkit-linear-gradient(top,#ffffff,#ffffff);
	background-image:linear-gradient(to bottom,#ffffff,#ffffff);
	-webkit-background-size:100% 5px;
	background-size:100% 5px;
	background-repeat:no-repeat;
	background-position:center;
}

                        
↑上面代码改变,会自动显示代码结果 jQuery调用版本:2.0.0
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