CSS3, Search, WP/CP | Type: CSSHTML5 Toggle Search

First, add HTML5 support to functions.php:

add_theme_support('html5', array('search-form'));

HTML(if HTML5 support)

<form role="search" method="get" class="search-form" action="<?php echo home_url( '/' ); ?>">
    <label>
        <span class="screen-reader-text">Search</span>
        <input type="search" class="search-field" placeholder="Use enter key to search" value="" name="s" title="Search" />
    </label>
    <input type="submit" class="search-submit" value="Search" />
</form>

CSS

.site-header .search-form { position: absolute; right: 200px; top: 200px; }

.site-header .search-field { background-color: transparent; background-image: url(images/search-icon.png); background-position: 5px center; background-repeat: no-repeat; background-size: 24px 24px; border: none; cursor: pointer; height: 37px; margin: 3px 0; padding: 0 0 0 34px; position: relative; -webkit-transition: width 400ms ease, background 400ms ease; transition: width 400ms ease, background 400ms ease; width: 0; }

.site-header .search-field:focus { background-color: #fff; border: 2px solid #c3c0ab; cursor: text; outline: 0; width: 230px; }

.search-form .search-submit {  display:none; }