Allow the user to increase font size

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My site is very small, and plain - it will mostly be text (for now). I
have used a good mix of css in the design.

With usability in mind I would like to add some specific functionality
(with the vision impaired in mind).

I would like to allow the user/reader of the web site the ability to
select another font size, say from a drop downbox. This would increase
the size of any text between paragraph tags, or in table data tags.
This device is not something that is a built in option from the
browser, but instead it is something right on the web page (i.e.
something I created).

Is this something that is done in the html or the css? Can you give any
hints on where I can start?

Thanks in advance.

Re: Allow the user to increase font size

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Every browser I have ever used contains its own features that allow
the user to change font size.  For example, go to View - Text Size in
either IE or Firefox, and you can change the font size of any HTML
page you are viewing.


Center For Practical Self Defense
Riverside, California

Re: Allow the user to increase font size

In our last episode,
the lovely and talented eomer
broadcast on comp.infosystems.www.authoring.html:

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What graphical browser doesn't have this feature (both in a
toolbar selection and a keyboard shortcut)?  Ctrl+ does it for

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Why?  If you write portable html, you are trying to reinvent the

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This would seem to be a job for a scripting language.

Lars Eighner /
     "I have never made but one prayer to God, a very short one: 'O Lord,
        make my enemies ridiculous.' And God granted it."  --Voltaire

Re: Allow the user to increase font size

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I don't know what browsers *you've* been using, but every browser I'm aware
of *does* have such an option.


Cocoa programming in Perl:
Hire me! My resume:

Re: Allow the user to increase font size

eomer wrote:
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   Browsers already do this. The only exception for GUI-based browsers is:
- Internet Explorer, and
- Your CSS specifies font sizes in either px or pt units.
Solution: Change the font-size specification to use % or em.

jmm (hyphen) list (at) sohnen-moe (dot) com
(Remove .AXSPAMGN for email)

Re: Allow the user to increase font size

On Sat, 3 Dec 2005, Jim Moe wrote:

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In this regard, IE is behaving to specification.  The fault lies with
the author (for proposing inappropriate units), not with the

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Indeed.  And read a briefing such as
to understand what value to aim for when using these units.


[1] To go into more detail: IE isn't without its many faults, but
its insistence on treating CSS absolute size units as absolute size
units does not seem to be rateable as a fault.

- IE is defective (as measured against the CSS specification) by not
calibrating the pt and px units in the way that's laid down by CSS.  
But then, most other browsers suffer from this failing too, and even
those which support calibration, are rarely adjusted by their users,
who (not surprisingly) are more interested in readability than in
pedantic conformance to the absolute size definitions of CSS.

- IE is also, arguably, defective in hiding away the option for users
to overrule such silly size specifications when they're causing
trouble.  It's not in the fonts menu, where most people seem to look
for it before giving up: it's in the Accessibility menu instead.


It seems that MS Office positively *insists* on setting absolute font
sizes in the HTML which it generates.  Even when its "filter for web
use" (whatever it's exactly called) option is used.  Grrrr.

Re: Allow the user to increase font size

Alan J. Flavell wrote:
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Well, since technically the CSS makes _suggestions_, even when using
absolute units, and since the user should come first, one might argue
that IE is at fault for not honouring the user's request to override
what the CSS suggests.

Re: Allow the user to increase font size

On Sat, 3 Dec 2005, C A Upsdell and MISSINGcupsdellXXX"TERMINATOR wrote:

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Point taken, although I'd tend to call them "proposals" ...

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Er, no: with CSS the user *has the last word*.  But as long as CSS is
being implemented, it has to be implemented *to specification*, not to
someone's misguided let's-do-what-the-author-should-have-intended

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Far be it from me to leap to defence of IE, but, as I already said, it
*does* implement a user override.  Its fault is that this override is
hidden away in a relatively obscure place.

The IE menu "View->Text Size" is not meant to be an override: it sets
an initial value, which is correctly overridden by an author
stylesheet - in the way that the CSS specification defines (i.e user
agent stylesheets have the lowest importance).  See 6.4.1.

If the user wants to *override* that behaviour - which they have every
right to do - then they have to find the appropriate override.  
Merely changing the browser defaults has no influence on IE's
honouring absolute size units.  In fact, someone more pedantic than me
would, I think, be entitled to fault other browsers for allowing such
violations of the absolute size units in ways that don't seem to
conform to the CSS specification.

I say again, the *author* is at fault for requesting absolute size
units, in flagrant violation of what the CSS specification tells them:

  " Absolute length units are only useful when the physical properties
  of the output medium are known. "

(see 4.3.2).  

The user options at that point would be to *override* the author
stylesheet, or to cascade it with a user stylesheet which is stronger
than the author's inappropriate size specifications (i.e "user
important" in the terms of 6.4.1).  Allowing the absolute size units
to be manually zoomed is neither one thing nor the other - no matter
how convenient it might seem to be.

IE *does* offer the override option, as I said before: the fault is
that the option is hidden away in the Accessibility menu.  (Doubtless
some bookmarklet or custom toolbar is available to make it more easily
reachable, but that's outside the scope of this comment.)


Re: Allow the user to increase font size

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But you would be wrong. CSS is overrideable by design, but when applying an
author style sheet, it must be applied correctly. If you interpret a
browser's font size control as applying a user style sheet, then its effect
should be clearly documented in CSS terms (and in Opera or Firefox, it
isn't), and this would be a somewhat unnatural interpretation. In particular,
using the author style sheet's font size settings and applying some increase
or decrease to them is weird - not even describeable in CSS terms.

IE _does_ let the user override pixel-valued settings, when a user style
sheet is applied and it uses !imporant. This is admittedly inconvenient to
users, and most users don't know about it, but it's the CSS way. (The real
improvement that would be needed is nice support to easy creation of a user
style sheet in the browser.) IE also lets the user override _all_ font
settings on a page, but that's a different story.

Yucca, /
Pages about Web authoring:

Re: Allow the user to increase font size

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Opera doesn't have a font size control (although you could use a user
style - I use "body { font-size:100% !important}"). What it does have
is a zoom feature that works on all content, not just text.

Well, there is also the "minimum point size" setting, for avoiding
completely unreadable text (before zooming). That's not something you can
set with standard CSS, but you could just as well say that it's due to
the virtual declaration "-o-min-font-size:6pt;".

Lasse Reichstein Nielsen  -
 DHTML Death Colors: <URL:
  'Faith without judgement merely degrades the spirit divine.'

Re: Allow the user to increase font size

eomer wrote:
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I have three buttons on the toolbar of my browser: Font-, Font+,
and Font=.  Obviously, the first two decrease and increase all the
displayed font sizes of the pages I am viewing.  The third button
restores the page to its original font sizes.  Note that when I say
"all the displayed font sizes", all are changed proportionally.
Thus, with Font-, fonts that are 2em remain twice the size of the
other fonts (albeit smaller than they were); and with Font+, fonts
that are 90% remain 10% smaller than the other fonts.  

What I resent are Web pages where use of these buttons corrupts the
display.  An example of that is in the individual news articles at
<URL: .  (The home page seems to be
okay.)  To compensate, however, the Globe and Mail news article
pages have the buttons you seek.  


David E. Ross

I use Mozilla as my Web browser because I want a browser that
complies with Web standards.  See <URL:>.

Re: Allow the user to increase font size

begin  quotation
 posted at 2005-12-03T02:43
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The user already have this ability, built into their browsers.

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Possible, certainly. There are a lot of things that are possible that
are incredibly bad ideas, though.

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