Re: PNG support in IE4

Rob (
Thu, 28 Aug 1997 00:04:50 -0500

Message-Id: <>
From: "Rob" <>
To: Ken Sykes <>
Date: Thu, 28 Aug 1997 00:04:50 -0500
Subject: RE: PNG support in IE4

On 27 Aug 97, wrote:

> >Also, IE4 does not send image/png in its HTTP-Accept headers, so
> >you can't do content negotiation either.  Finally, neither gamma
> >correction for color matching or partial transparency is supported.
> >In short, IE4 may claim to "support" PNG, but the claim is hollow.
> We send */* at the end of our accept header list so there shouldn't be
> anything preventing PNG files from being sent.  I'm not familiar with

No! It's better if it includes image/png so that scripts will know to 
send inline PNG files which are smaller than GIFs. A */* doesn't tell 
the server that support for the format is built in.

I have a simple script I've used on my site to check the accept
types and decide whether to send a GIF, PNG or JPEG (actually using
a Location: header) depending on what the browser claims to support
and the smallest of file types.

The only thing that's kept me from implementing it is because the
major browsers (up until now, at least) don't have PNG support built
in.   (UdiWWW sends the proper accept headers, but PNG support is
buggy and it's no longer being updated.)

One could have a script that checks the Agent-name, but this is a 
pain to keep up-to-date with, doesn't help with 'spoofing' agents and 
just plain-old-isn't-the-proper-way-to-do-things.

> all the issues here but our current list is the result of compatibility
> testing over the last 6-12 months.  My understanding is the accept
> headers are generally ignored.  We won't be changing the list for IE4,

Most headers are ignored since most scripts and servers don't need to 
do much with them. But ignoring them in developing a browser makes 
them useless and limits what one can do.

> but if you have comments on accept header processing please pass them on
> so we can consider them for IE5.

How hard is it to specify a few built-in types in the headers? Can it 
be header than changing a line or two in the source code?

Robert Rothenburg Walking-Owl (
(Se habla PGP.)