Here's the CSS code that I'd use:
#add {
padding: 17px;
padding-left: 55px;
width: 300px;
border: 1px solid #f5f5f5;
font-size: 13px;
color: gray;
background-image: url('http://i47.tinypic.com/r02vbq.png');
background-repeat: no-repeat;
background-position: left center;
outline: 0;
}
Note: I added a lot of extra codes to make the search box look better, the necessary code to make the search box apear is padding-left, background-image:url, background-repeat and background-position. Replace "http://i47.tinypic.com/r02vbq.png" with whatever search icon you want.
It's also important to know that now in HTML5, most browsers render
with a search icon. The input type search makes it a search box, with a "x" button to clear, and adding "results" also displays a search box. Of course you could also add an x button with CSS and JavaScript to a regular search box. It's also important to note that input type search allows very little styling. Demo on Safari on a Mac:
Tell me if this helps you, and make sure to mark as the answer. :)