bullet image in front of title in sidebar widget

I’m using a new theme I just installed on my blog, I have a sidebar widget that displays the last 5 posts but I wanted it to have a little arrow in front of each title to make them stand out so I added this to the css:

ul.group li ul {
padding-left: 18px;
background: url(img/arrow.gif) no-repeat 0px 3px;
}

under this part of the stylesheet:

ul.group {
float: left;
margin: 0 0 0 10px;
overflow: hidden;
padding: 0;
width: 150px;
}

It displays an arrow in front of the first titles post but not for the second, third or none of the rest, any suggestions?

Much appreciated =)