How do I format a sidebar for a static homepage so it is displayed inline rather than vertical?

I recently created a php file for an additional, customizable homepage sidebar for my static homepage. I am now trying to format it so it is displayed inline (in a vertical row) rather than horizontally, but I'm having difficulty. Right now I am editing internally within the php file, because additions to my stylesheet aren't helping. Would you be able to assist me? My code is as follows:
<style>
#sidebar {
position:fixed;
bottom: 0;
width:100%;
height:350px;
left:0;
}
#sidebar ul li {
float:left;
position: relative;

}

</style>
<div id="sidebar">

    <?php
    if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('homepage-sidebar') ) :
    endif; ?>

</div>