CSS div shrinks on zoom out

Question

I am using a div for my site's breadcrumbs. It remains a constant size on the actual size of browser window and on zoom in. But on zoom out the div is shrinking.

This is the code am using. Do I require an edit in it somewhere?

    <style>

.breadcrumb { 
        list-style: none; 
        overflow: hidden; 
        font: 18px Lucida Sans Unicode;
        text-align: center;
}
.breadcrumb li { 
        float: left;

}
.breadcrumb li a {
        color: white;
        text-decoration: none; 
        padding: 11px 0 11px 55px;
        background:  #327ea4;                   /* fallback color */
        background:  #327ea4; 
        position: relative; 
        display: block;
        float: left;
        width: 15.12em;
        /*width: 15.1185em;*/
        cursor: default;
        border-top-left-radius: .4em;
        pointer-events: none;
}
.breadcrumb li a:after { 
        content: " "; 
        display: block; 
        width: 0; 
        height: 0;
        border-top: 50px solid transparent;           /* Go big on the size, and let overflow hide */
        border-bottom: 50px solid transparent;
        border-left: 30px solid  #327ea4;
        position: absolute;
        top: 50%;
        margin-top: -50px; 
        left: 100%;
        z-index: 2; 
}   
.breadcrumb li a:before { 
        content: " "; 
        display: block; 
        width: 0; 
        height: 0;
        border-top: 50px solid transparent;           /* Go big on the size, and let overflow hide */
        border-bottom: 50px solid transparent;
        border-left: 30px solid white;
        position: absolute;
        top: 50%;
        margin-top: -50px; 
        margin-left: 1px;
        left: 100%;
        z-index: 1; 
}   
.breadcrumb li:first-child a {
        padding-left: 30px;
}
.breadcrumb li:nth-child(2) a       { background:        #7fc1ec; color: #327ea4; cursor: default;}
.breadcrumb li:nth-child(2) a:after { border-left-color: #7fc1ec; color: #327ea4; cursor: default;}
.breadcrumb li:nth-child(3) a       { background:        #7fc1ec; color: #327ea4; cursor: default;}
.breadcrumb li:nth-child(3) a:after { border-left-color: #7fc1ec; color: #327ea4; cursor: default;}
.breadcrumb li:nth-child(4) a       { background:        #7fc1ec; color: #327ea4; cursor: default;}
.breadcrumb li:nth-child(4) a:after { border-left-color: #7fc1ec; color: #327ea4; cursor: default; }
.breadcrumb li:last-child a {
        /*background: white !important;*/
        /*color: black;*/
        pointer-events: none;
        cursor: default;
        border-top-right-radius: .4em;
}
.breadcrumb li:last-child a:after { border: 0; }
    </style>

<div style="width:75em;" oncontextmenu="return false"  >
    <ul class="breadcrumb">
        <li><a href="#">Step 1</a></li>
        <li><a href="#">Step 2</a></li>
        <li><a href="#">Step 3</a></li>
                    <li><a href="#">Step 4</a></li>
    </ul>

</div>

Thanks in advance.

Answer 1

when you define the height or width of an element in EM's, like in the following snippet...

.breadcrumb li a {
        color: white;
        text-decoration: none; 
        padding: 11px 0 11px 55px;
        background:  #327ea4;
        background:  #327ea4; 
        position: relative; 
        display: block;
        float: left;
        width: 15.12em; /* <-- RIGHT HERE */
        cursor: default;
        border-top-left-radius: .4em;
        pointer-events: none;
}

... you're actually binding the the size of the element to the font-size for that element.

When you increase the browser "zoom", all that's happening is in the font size is being increased (in pixels).

Example:

font-size: 10px, therefore width: 2em == width: 20px.

Zoom (increase font-size)

font-size: 12px, therefore width: 2em == width: 24px.