Código HTML.
<style>
#search-box {
position: relative;
width: 100%;
margin: 0;
}
#search-form
{
height: 42px;
border: 1px solid #ebebeb;
background-color: #fff;
overflow: hidden;
}
#search-text
{
font-size: 14px;
color: #ddd;
border-width: 0;
background: transparent;
height: 42px;
line-height: 42px;
}
#search-box input[type="text"]
{
width: 90%;
padding: 11px 0 12px 1em;
color: #333;
outline: none;
}
#search-button {
position: absolute;
top: 0;
right: 0;
height: 42px;
width: 80px;
font-size: 14px;
color: #fff;
text-align: center;
line-height: 42px;
border-width: 0;
background-color: #fb4834;
cursor: pointer;
}
</style>
<br />
<div id="search-box">
<form action="/search" id="search-form" method="get" target="_top">
<input id="search-text" name="q" placeholder="buscar..." type="text" />
<button id="search-button" type="submit"><i class="fa fa-search"></i></button>
<br />
<br />