SOURCE

<form>
      <input type="search" placeholder="搜索">
</form>

input {
	outline: none;
}
input[type=search] {
	-webkit-appearance: textfield;
	-webkit-box-sizing: content-box;
	font-size: 100%;
}
input::-webkit-search-decoration,
input::-webkit-search-cancel-button {
	display: none;
}

input[type=search] {
	background: #ededed url(http://webdesignerwall.com/demo/expandable-search-form/images/search-icon.png) no-repeat 9px;
	border: solid 1px #ccc;
	padding: 9px 10px 9px 32px;
	width: 55px;
	
	-webkit-border-radius: 10em;
	-moz-border-radius: 10em;
	border-radius: 10em;
	
	-webkit-transition: all .5s;
	-moz-transition: all .5s;
	transition: all .5s;
}
input[type=search]:focus {
	width: 130px;
	background-color: #fff;
	border-color: #6dcff6;
	
	-webkit-box-shadow: 0 0 5px rgba(109,207,246,.5);
	-moz-box-shadow: 0 0 5px rgba(109,207,246,.5);
	box-shadow: 0 0 5px rgba(109,207,246,.5);
  
  
}