[css] IE7 Z-Index Layering Issues

I've isolated a little test case of IE7's z-index bug, but don't know how to fix it. I have been playing with z-index all day long.

What is wrong with z-index in IE7?

Test CSS:

input {
    border: 1px solid #000;
}

div {
    border: 1px solid #00f;
}

ul {
    border: 1px solid #f00;
    background-color: #f00;
    list-style-type: none;
    margin: 0;
    padding-left: 0;
    z-index: 1000;
}

li {
    color: #fff;
    list-style-type: none;
    padding-left: 0;
    margin-left: 0;
}

span.envelope {
    position: relative;
}

span.envelope ul {
    position: absolute;
    top: 20px;
    left: 0;
    width: 150px;
}

Test HTML:

<form>
  <label>Input #1:</label>
  <span id="envelope-1" class="envelope">
    <input name="my-input-1" id="my-input-1" />
      <ul>
        <li>item</li>
        <li>item</li>
        <li>item</li>
        <li>item</li>
      </ul>
  </span>
  <br><br>
  <label>Input #2:</label>
  <span id="envelope-2" class="envelope">
    <input name="my-input-2" id="my-input-2" />
  </span>
</form>

It looks like not a ie bug, just for diffrent understanding to the css standard. If outside container is not specified the z-index, but the inner element specified a higher z-index. So the container's sibling maybe overlay the high z-index element. Even if like that, it only occurs in IE7, but IE6, IE8 and Firefox is ok.

I found that I had to place a special z-index designation on div in a ie7 specific styelsheet:

div { z-index:10; }

For the z-index of unrelated divs, such as a nav, to show above the slider. I could not simply add a z-index to the slider div itself.

This bug seems to be somewhat of a separate issue than the standard separate stacking context IE bug. I had a similar issue with multiple stacked inputs (essentially a table with an autocompleter in each row). The only solution I found was to give each cell a decreasing z-index value.

If you wanna create dropdown menu and having a problem with z-index, you can solve it by creating z-indexes of same value (z-index:999; for example).. Just put z-index in parent and child div's and that will solve problem. I solve the problem with that. If i put different z-indexes, sure, it will show my child div over my parent div, but, once i want to move my mouse from menu tab to the sub-menu div (dropdown list), it dissapear... then i put z-indexes of same value and solve the problem..

If the previously mentioned higher z-indexing in parent nodes wont suit your needs, you can create alternative solution and target it to problematic browsers either by IE conditional comments or using the (more idealistic) feature detection provided by Modernizr.

Quick (and obviously working) test for Modernizr:

Modernizr.addTest('compliantzindex', function(){
    var test  = document.createElement('div'),
        fake = false,
        root = document.body || (function () {
            fake = true;
            return document.documentElement.appendChild(document.createElement('body'));
        }());

    root.appendChild(test);
    test.style.position = 'relative';
    var ret = (test.style.zIndex !== 0);
    root.removeChild(test);

    if (fake) {
        document.documentElement.removeChild(root);
    }

    return ret;
});

http://www.vancelucas.com/blog/fixing-ie7-z-index-issues-with-jquery/

$(function() {
var zIndexNumber = 1000;
$('div').each(function() {
    $(this).css('zIndex', zIndexNumber);
    zIndexNumber -= 10;
});
});

In IE positioned elements generate a new stacking context, starting with a z-index value of 0. Therefore z-index doesn’t work correctly.

Try give the parent element a higher z-index value (can be even higher than the child’s z-index value itself) to fix the bug.

I solved it by using the developer tools for IE7 (its a toolbar) and adding a negative z-index to the container of the div that will be below that the other div.

I encountered this issue, but on a large project where HTML changes had to be requested and became a whole issue, so I was looking for a pure css solution.

By placing position:relative; z-index:-1 on my main body content my header drop down content suddenly displayed above the body content in ie7 (it was already displaying without issue in all other browsers and in ie8+)

The problem with that was then this disabled all hover and click actions on all content in the element with the z-index:-1 so i went to the parent element of the whole page and gave it a position:relative; z-index:1

Which fixed the issue and retained the correct layering functionality.

Feels a bit hacky, but worked as required.

In IE6 in general, certain UI-elements are implemented with native controls. These controls are rendered in a completely separate phase (window?) and always appear above any other controls, regardless of z-index. Select-boxes are another such problematic control.

The only way to work-around this issue is to construct content which IE renders as a seperate "window" - i.e. you can place a selectbox over a textbox, or, more usefully, an iframe.

In short, you'll need to put "on-hover" like things such as menu's in an iframe in order to let IE place these above built-in UI controls.

This should have been fixed in IE7 (see http://blogs.msdn.com/ie/archive/2006/01/17/514076.aspx) but perhaps you're running in some kind of compatibility mode?