text align for display block element doesn't work in ie5,6,7

Question

i have a simple menu list...

---

<ul>
  <li><a href="#">Մեր Մասին</a></li>
  <li><a href="#">Դասընթացներ</a></li>
  <li><a href="#">Գրանցվելու կարգը</a></li>
  <li><a href="#">Հետադարձ կապ</a></li>
</ul>

and CSS:

#menus a
{
    margin: 0;
    padding: 3px 0 0 0;
    color: white;
    font-size: 15px;
    display: block;
    width: 160px;
    text-decoration: none;
    text-align: center;
}
#menus ul
{
    margin: 0 0 0 119px;
    list-style: outside none;
}
#menus ul li
{
    float: left;
}

but in ie5,6,7 text align="center" doesn't work.

any ideas?

(i also tried to set margin auto for a element but it doesn't work too)

Thanks