font size smaller than default creates accessibility and usability difficulties

Bug #523189 reported by Kiri on 2010-02-17
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Launchpad itself
Curtis Hovey

Bug Description

When a font is displayed at a size smaller than the user's default font size, that creates a usability and accessibility problem. As point 3 of Canonical's philosophy states:
3. Every computer user should be given every opportunity to use software, even if they work under a disability.

However, this is even more widespread a problem than only affecting those who's eyesight is so poor that they count as disabled.

About my environment:
screen DPI according to GNOME: 120 (Bug #157398, Discussed in Bug #311614)
screen DPI according to X Windows: 96 (Bug #201032)
GNOME font size: 12point
Firefox 3.6 Font size: 20pixel

Relevant information about the CSS properties is at

Note, that last i checked, some years ago, the Mozilla sizing of images in em units was incorrect. It made 1.2em be the full hight of what is actually 1em. The Wikipedia entry on em is illuminating.

Looking at
There are some things which are going to make it difficult to ensure that all content sufficiently sized, such as:


The good thing about these is that they are relative sizes. It is possible, if sufficient care is taken, to write the web pages so that none of the content gets shrunk so that it is smaller than the user's default font size. If too many of these kind of size reductions are embedded in one another, the result will be a font which is too small.

It is probably easier to get it right by specifying all sizes in em units.
See also:
Chapter 4
The amazing em unit and other best practices

Here is a good example from the same LaunchPad CSS file.

Related branches

Kiri (kiri) wrote :

A helpful way to identify fonts which are too small is to disable antialiasing for fonts smaller than default.

Curtis Hovey (sinzui) wrote :

This bug may be fixed when style.css is removed. The font-size cited here from from that file. The stylesheet is deprecated because it does not use YUI-compatiable font-sizes

affects: launchpad → launchpad-foundations
Gary Poster (gary) on 2010-03-02
Changed in launchpad-foundations:
status: New → Triaged
importance: Undecided → Low
tags: added: css
Jonathan Lange (jml) on 2010-03-12
affects: launchpad-foundations → launchpad-web
Curtis Hovey (sinzui) wrote :

This bug cannot be fixed until Launchpad abandons YUI-Font, or YUI-Font switches to em, px, or pt.

Launchpad uses YUI-Font to normaize font sizes across browser and OSes. It stipulates that all font sizes must be expressed in specific precentages to get the expected point size. This is difficult to use because browsers know that percentages are relative; nesting classes have surprising results.

The attached image shows that developers cannot specify the intended font size.

Launchpd pages are constructed from many html fragments. The fragments are intended to be usable in many places on a page and display the the same way. Launchpad cannot use percentages for font-size.

Curtis Hovey (sinzui) wrote :

I started a branch that sets the default em size to about 10px (based on the default 16pt font used by browsers). I then switched to ems using 1.2em as the default font. I can see a lot of madness in the pages. There is text that is too small. There are some odd changes in font size. I think the solution will be to reduce the number of locations that font-size is set to get a small set of sizes, between 5 and 7 sizes.

Changed in launchpad:
assignee: nobody → Curtis Hovey (sinzui)
status: Triaged → In Progress

On Wed, Feb 16, 2011 at 2:48 PM, Curtis Hovey
<email address hidden> wrote:
> I think the solution will be to reduce the number of locations
> that font-size is set to get a small set of sizes, between 5 and 7
> sizes.

We should follow the sizes outlined on page 16 of

Curtis Hovey (sinzui) wrote :

I certainly agree. I have tried updating the sizes twice. Last night a came close to succeeding. h1 and h2 in the Lp header break the layout; I need to think about whitespace between sections.

Kiri (kiri) wrote :

How do you file a bug against the Ubuntu Web Guidelines ?

Launchpad QA Bot (lpqabot) wrote :
Changed in launchpad:
milestone: none → 11.03
tags: added: qa-needstesting
Changed in launchpad:
status: In Progress → Fix Committed
Curtis Hovey (sinzui) on 2011-03-01
tags: added: qa-ok
removed: qa-needstesting
William Grant (wgrant) on 2011-03-02
Changed in launchpad:
status: Fix Committed → Fix Released
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