How to align the tooltip the natural style: right bottom of the mouse pointer?
Tooltip with Im
One way to do this without JS is to use the hover action to reveal a HTML element that is otherwise hidden, see this codepen:
http://codepen.io/c0un7z3r0/pen/LZWXEw
Note that the span that contains the tooltip content is relative to the parent li. The magic is here:
ul#list_of_thrones li > span{
display:none;
}
ul#list_of_thrones li:hover > span{
position: absolute;
display:block;
...
}
As you can see, the span is hidden unless the listitem is hovered over, thus revealing the span element, the span can contain as much html as you need. In the codepen attached I have also used a :after element for the arrow but that of course is entirely optional and has only been included in this example for cosmetic purposes.
I hope this helps, I felt compelled to post as all the other answers included JS solutions but the OP asked for a HTML/CSS only solution.