MENU DISPLAY PROBLEMS

So I have a menu from ul and li, and it looks something like this at page load:

but when i click each menu and executed the code this happens:

what should i do? here's my CSS:

#menu-centered {
    padding: 0px;
    margin-bottom: 0px;
}
#menu-centered ul {
    margin: 0;
    padding: 0;
    height: 99px;
    width: 开发者_如何转开发603px;
}
#menu-centered li {
    display: inline;
    list-style: none;
    padding: 0px;
    background: url(images/menu1.png) no-repeat right top;
}
#menu-centered a {
    border-style: none;
    border-color: inherit;
    border-width: medium;
    display: block;
    margin-right: 0;
    padding: 20px 30px 0px 30px;
    text-decoration: none;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 16px;
    font-weight: normal;
    color: #FFFFFF;
    height: 68px;
    width: 130px;
    text-align: center;
}
#menu-centered a:hover {
    background: url(images/menu2.png) no-repeat right top;
}

and here's my html code for the menus:

<div id="menu-centered">
<ul>
<li> <a href="javascript:Clikbtn1()" >MENU1</a></li>
<li><a href="javascript:Clikbtn2()">MENU2</a></li>
<li><a href="javascript:Clikbtn3()">MENU3</a></li>
</ul>
</div>

Please help. Thanks

Your menus need some LoVe and HAte. In other words you need to create all four of the important link pseudoselectors to avoid letting browsers destroy your layout by applying the default active pseudoslector.

Define a:link, a:visited, a:hover and a:active for your menu, in that order exactly.