How to create vertical menu with sub menu using CSS

HTML Part:

<div id="menuwrapper">
    <ul>
        <li><a href="#">Home</a></li>
        <li><a href="#">Products</a>
            <ul>
                <li><a href="#">Product 1</a>
                    <ul>
                        <li><a href="#">Sub Product 1</a></li>
                        <li><a href="#">Sub Product 2</a></li>
                        <li><a href="#">Sub Product 3</a></li>
                    </ul>
                </li>
                <li><a href="#">Product 2</a></li>
                <li><a href="#">Product 3</a></li>
            </ul>
        </li>
        <li><a href="#">About Us</a>
            <ul>
                <li><a href="#">Faqs</a></li>
                <li><a href="#">Contact Us</a></li>
                <li><a href="#">Where are we?</a></li>
            </ul>
        </li>
        <li><a href="#">Help</a>
    </ul>
</div>


CSS Part:
/* We remove the margin, padding, and list style of UL and LI components */
#menuwrapper ul, #menuwrapper ul li{
    margin:0;
    padding:0;
    list-style:none;
}

/* We apply background color and border bottom white and width to 150px */
#menuwrapper ul li{
    background-color:#7f95db;
    border-bottom:solid 1px white;
    width:150px;
    cursor:pointer;
}

/* We apply the background hover color when user hover the mouse over of the li component */
#menuwrapper ul li:hover{
    background-color:#6679e9;
    position:relative;
}

/* We apply the link style */
#menuwrapper ul li a{
    padding:5px 15px;
    color:#ffffff;
    display:inline-block;
    text-decoration:none;
}

/**** SECOND LEVEL MENU ****/
/* We make the position to absolute for flyout menu and hidden the ul until the user hover the parent li item */
#menuwrapper ul li ul{
    position:absolute;
    display:none;
}

/* When user has hovered the li item, we show the ul list by applying display:block, note: 150px is the individual menu width.  */
#menuwrapper ul li:hover ul{
    left:150px;
    top:0px;
    display:block;
}

/* we apply different background color to 2nd level menu items*/
#menuwrapper ul li ul li{
    background-color:#cae25a;
}

/* We change the background color for the level 2 submenu when hovering the menu */
#menuwrapper ul li:hover ul li:hover{
    background-color:#b1b536;
}

/* We style the color of level 2 links */
#menuwrapper ul li ul li a{
    color:#454444;
    display:inline-block;
    width:120px;
}

/**** THIRD LEVEL MENU ****/
/* We need to hide the 3rd menu, when hovering the first level menu */
#menuwrapper ul li:hover ul li ul{
    position:absolute;
    display:none;
}

/* We show the third level menu only when they hover the second level menu parent */
#menuwrapper ul li:hover ul li:hover ul{
    display:block;
    left:150px;
    top:0;
}

/* We change the background color for the level 3 submenu*/
#menuwrapper ul li:hover ul li:hover ul li{
    background:#86d3fa;
}

/* We change the background color for the level 3 submenu when hovering the menu */

#menuwrapper ul li:hover ul li:hover ul li:hover{
    background:#358ebc;
}

/* We change the level 3 link color */
#menuwrapper ul li:hover ul li:hover ul li a{
    color:#ffffff;
}

/* Clear float */
.clear{
    clear:both;

}