在水平菜单下移动页面内容

Question

I have this css for my horizontal menu:

when you hover over the links and a sub menu appears, it shows the sub menu but the page content below moves down slightly.

any ideas?

fiddle here: http://jsfiddle.net/XwDTt/1/

nav {
    margin: 0 auto; 
    text-align: center;
}

nav ul ul {
    display: none;
}

nav ul li:hover > ul {
    display: block;
}

nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: inline-block;
    vertical-align: top;
}

nav ul li {
    float: left;
    margin: 0;
    padding: 0;
}

nav ul li:hover a {
    color: #000000;
    margin-bottom:5px;
    border-top: 1px solid #000000;
    border-bottom: 1px solid #000000;
}

nav ul li a {
    display: block; 
    padding: 5px 15px;
    color: #000000;
    text-decoration: none;
    background-color: #eeeeee;
}       

nav ul ul {
    border-radius: 0px;
    padding: 0;
    position: absolute;
}

nav ul ul li {
    float: none; 
    position: relative;
}

nav ul ul li a {
    color: #000000;
}

nav ul ul li a:hover {
    color: #666666;
}

nav ul ul ul {
    position: absolute;
    top:0;
}

Answer 1

change this:

nav ul li:hover a {
    color: #000000;
    margin-bottom:5px;
    border-top: 1px solid #000000;
    border-bottom: 1px solid #000000;
 }

into this :

nav ul li:hover a {
    color: #000000;
    margin-bottom:5px;
    border-top: 1px solid #000000;
    border-bottom: 1px solid #000000;
    position:relative;
    top:-1px;
}

Answer 2

There are two points here:

1. When you add a border to an element, it often increases the height of the element. You could use a transparent border by default.
2. Instead of setting a margin property on anchor tags, you could use the property on the sub-menu list-items, which are positioned absolute and doesn't affect the document normal flow.

Use the following:

nav ul li:hover a {
    color: #000000;
    border-top: 1px solid #000000;
    border-bottom: 1px solid #000000;
}

nav ul li:hover li {
    margin-top: 5px; /* <-- add margin to sub-menu items */
}

nav ul li a {
    display: block; 
    padding: 5px 15px;
    color: #000000;
    text-decoration: none;
    background-color: #eeeeee;

    border-top: 1px solid transparent;    /* <-- Set a transparent border */
    border-bottom: 1px solid transparent; /* <-- Set a transparent border */    
}

JSFiddle Demo

Answer 3

i think this one is the simplest

nav {
    margin: 0 auto; 
    text-align: center;
    height:30px;    /* add height to your nav tag */
}

Answer 4

You are adding border on hover. You should have transparent borders by default... And margin too.

nav ul li a {
   display: block; 
   margin-bottom:5px;
   padding: 5px 15px;
   color: #000000;
   text-decoration: none;    
   background-color: #eeeeee;
   border-top: 1px solid #eeeeee;
   border-bottom: 1px solid #eeeeee;
}       

http://jsfiddle.net/XwDTt/3/

Answer 5

Or you can just set the height of li elements:

nav ul li {
    float: left;
    margin: 0;
    padding: 0;
    height:30px;
}

Answer 6

Solution 1:

nav ul li:hover a {
    color: #000000;
    /*margin-bottom:5px comment these
    border-top: 1px solid #000000;
    border-bottom: 1px solid #000000;*/
}

Solution 2:

nav ul li:hover a {
    color: #000000;
    /*margin-bottom:5px comment this line only */
    border-top: 1px solid #000000;
    border-bottom: 1px solid #000000;;
}

and add this line:

nav ul li a {
        margin-bottom:5px;
        border-top:1px solid #fff;
        border-bottom:1px solid #fff;
}