Dealing with display: block

So I’ve been working on trying to get display: block to work with my menu, but it hasn’t been working with me at all. I tried adding it to this part of the code:
#menu ul ul li a {
color: #ffffff;
text-decoration: none;
}
However, in doing so, I keep getting line breaks before each of the links that I’ve been using. And I’m pretty sure the container is set up right as well:
#menu ul {
list-style-type: none;
margin: 0px;
padding: 0px;
}
Anyone know how I can fix this?