大家帮我看看这个div+css样式的问题，是怎么回事啊？

   <div id="all">
    <div id="top">
        <div id="top1">
            <img src="images/1.JPG" alt="美信联创" />
        </div>
        <div id="top2" >
            <div id="top1left" ></div>
            <div id="top2right">
                <div>
                    <ul>
                        <li><a href="ComSever.aspx">客户服务</a></li>
                        <li><a href="BesinessMain.aspx">商务方案</a></li>
                        <li><a href="#">联系购买</a></li>
                        <li><a href="Interview.aspx">人才招聘</a></li>
                        <li><a href="#">商务论坛</a></li>
                        <li><a href="AboutCom.aspx">关于我们</a></li>
                    </ul>
                </div>
            </div>
        </div>
         <div id="top3" ></div> 
    </div>
  
    <div id="content">
        <asp:contentplaceholder id="ContentPlaceHolder1" runat="server">
        </asp:contentplaceholder>
    </div>
    </div>------------------------------------body 
{
text-align:center;
}#top2right li
{
font-size:12px;
text-align:center;
display:block; 
    float:left;
cursor:pointer;
margin:0px 0px 0px 0px;
padding:0px 0px 0px 0px;
line-height:50px;
height:47px;
background:url('../images/3.jpg') no-repeat;
width:128px;
}#top2right ul
{
margin:0px;
list-style:none;
margin:0px 0px 0px 0px;
padding:0px 0px 0px 0px;
height:100%;
overflow:hidden;
}#top2left
{
 float:left;
}#top
{
margin:0px 0px 0px 0px;
float:left;
height:100%;
overflow:hidden;
padding:0px 0px 0px 0px;
position:relative;
}
#top1
{
float:left;
height:70px;
margin:0px 0px 0px 0px;
padding:0px 0px 0px 0px;
position:relative;
}
#top2 
{
float:left;
overflow:hidden;
position:relative;
margin:0px 0px 0px 0px;
padding:0px 0px 0px 0px;
height:100px;
width:97%;
position:relative;
vertical-align:middle;

}
#top1left
{
margin:0px 0px 0px 0px;
padding:0px 0px 0px 0px;
float:left;
background-image:url('../images/zx.jpg');
width:253px;
height:47px;
position:relative;}
#top3 
{
float:left;
margin:0px 0px 0px 0px;
width:1024px;
height:248px;
background-image:url('../images/ss.JPG');
position:relative;
}
#content
{
float:left;
text-align:center;
vertical-align:top;
overflow:hidden;
position:relative;
}现在的问题是： 
1，top2和 top3  之间总是有一处空白，不知道怎么让他调没有了？
2，所有的东西我想让他在页面的中央，但是现在所有的块都是左对齐的？