[Aetae]

transition:

<div id="sidebar">
    <ul class="link_style">
    <li><a href="/">HTML5</a></li>
    <li><a href="/">CSS3</a></li>
</div>
<style>
a {
    margin-left:0px;
    transition: 0.6s margin-left;
}
a:hover {
    margin-left:10px;
}
</style>