Zoom bug in IE7/8 and Firefox caused by border

UPDATE:  As of Jan 2009, this bug is still appearing in the latest release of Firefox 3.5.7  The bug was fixed at some point in Firefox 3, but it has reappeared :(

After ranting on twitter for the last few hours, I realized it might be more helpful for the web development community to write a more thorough explanation of the bug that I’ve recently discovered.

This bug relates to both Internet Explorer 7/8 and Firefox 3.

The bug in action:


If you have a fixed width element containing floated elements that take up 100% of the that container’s width, and any of those elements have a border, zooming below 100% will cause the floats to break or wrap below the adjacent floated element. A small border will trigger the break quicker than a larger border.

Why nitpick?

This could actually cause a website to be unusable when zoomed down.  If you have a sidebar with navigation floated and that sidebar has a 1 pixel border… ouch.  Your navigation will probably wrap underneath your main area… probably below the wrap.  Site navigation gone.


This is the first set of divs. Just a container “a” with floated “b” and “c” inside of it.

<div class="a">
<div class="b">div b</div>
<div class="c">div c</div>

In the second set of divs, I’ve added a wrapper of “border” so that I can add a border to it and reduce its width (for proper box-model width total) with the CSS.

<!--add a "border" div to set .b border and reduce its width-->
<div id="border">
<div class="a">
<div class="b">div b</div>
<div class="c">div c</div>

The CSS:

.a {
.b {
width: 100px;
.c {
#border .b{
border: 1px solid black;

Below is a screenshot of how the code renders at 100% zoom in IE7/8 as well as Firefox 3:

code rendered at 100% zoom in IE7/8 and Firefox (acutally... all modern browsers :P)

Code rendered at 100% zoom in IE7/8 and Firefox (acutally... all modern browsers)

Now, here is what it looks like if you zoom down to anything below 100% (I’m using 99% here just so you can easily see the elements, but the results are similar for all zoom percentages below 100%)

code rendered at 99% zoom and below.  The floated div wraps.  This is the bug

Code rendered at 99% zoom and below. The floated div wraps. This is the bug

This is the simplest example I could think of. I spent hours working math on paddings/margins/borders trying to understand why my pages were breaking when zoomed down. I finally narrowed it down to the border. Can anyone confirm if this is a noted bug?

The Results

Here is the link again for you to test the bug.

It’s worth noting that the bug is not present in Opera, Chrome, or Safari. Also worth noting… zoom feature sucks anyway. Why won’t they trash it?

Is there a fix?

Unfortunately, my only suggestion is to not set the inside elements to exactly the width of their container.  Give em some breathn’ room.  If the page breaks at 25% zoom, I really don’t care.  But it should be able to at least zoom down 1 time :)

7 thoughts on “Zoom bug in IE7/8 and Firefox caused by border”

  1. I ran into the same bug in Firefox 3.5. So if it was fixed in 3.0, then it came back in Firefox 3.5. Anyways, in my particular setup I only had a one pixel left border and that caused issues when I zoomed out by one notch. Then, when I changed it to a 2 pixel border (again, only on the left), it didn’t have an issue until I zoomed out the page by 6 notches.

    My solution will be to get rid of the left border and replace it with a faux border using a background image.

  2. I have had the same problem as this and stumbled onto your blog in my search to solve this problem, though nothing came up but your blog post. I have eventually found a solution, not very pretty but what you need to do is set a negative margin-right on div C (large enough value to stop it from breaking the box) and that should stop div C breaking onto a new line.

  3. Wow, thanks so much for this. This issue has been driving me crazy. At least now I know what it is so I can go about finding a way around this bug. Thanks again for the work.

  4. “It’s worth noting that the bug is not present in Opera, Chrome, or Safari.”

    Just as an FYI, the bug is present in Chrome and Safari (at least the latest releases out now). You have to zoom out a few levels, but wrapping does still occur. Right now, it seems that Opera is the only browser that doesn’t suffer from this zoom-out/border issue.

    In any case, thanks for this post as it helped me determine that I can’t use borders on my navigation links.

  5. Thank you for identifying and explaining this problem!

    As for your (original author) comment:
    “Also worth noting… zoom feature sucks anyway. Why won’t they trash it?”

    I agree entirely if you mean zooming out (reducing the image).
    However, my old eyes often need to zoom in (enlarge) a page to read certain things where I need to know an exact number, etc. So I would like continued support for zooming in (which does not cause this problem anyway).
    Are there any known problems with zooming in to enlarge pages?

  6. @Bruce, no the bug is not triggered when you zoom in or “enlarge” pages. I agree, there is a need for zooming in. I see this need more now that I have a 27inch monitor where the native dpi makes things much smaller.

  7. This issue is in fact still present, but as far as I can tell, just in Firefox. The best solution I have found is the solution posted by thebob above. I have used this on multiple site designs with success.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>