![](https://csdnimg.cn/release/download_crawler_static/6312677/bg11.jpg)
This tag can be embedded in an anchor like anything else; when that happens, it becomes
an icon that’s sensitive to activation just like a regular text anchor.
Browsers should be afforded flexibility as to which image formats they support. Xbm
and Xpm are good ones to support, for example. If a browser cannot interpret a given
format, it can do whatever it wants instead (X Mosaic will pop up a default bitmap as a
placeholder).
This is required functionality for X Mosaic; we have this working, and we’ll at least be
using it internally. I’m certainly open to suggestions as to how this should be handled
within HTML; if you have a better idea than what I’m presenting now, please let me
know. I know this is hazy with regard to image format, but I don’t see an alternative than
to just say “let the browser do what it can” and wait for the perfect solution to come
along (MIME, someday, maybe).
This quote requires some explanation. Xbm and Xpm were popular graphics formats
on Unix systems.
“Mosaic” was one of the earliest web browsers. (“X Mosaic” was the version that ran
on Unix systems.) When he wrote this message in early 1993, Marc had not yet founded
the company that made him famous, Mosaic Communications Corporation, nor had
he started work on that company’s flagship product, “Mosaic Netscape.” (You may
know them better by their later names, “Netscape Corporation” and “Netscape
Navigator.”)
“MIME, someday, maybe” is a reference to content negotiation, a feature of HTTP
where a client (like a web browser) tells the server (like a web server) what types of
resources it supports (like image/jpeg) so the server can return something in the client’s
preferred format. “The Original HTTP as defined in 1991” (the only version that was
implemented in February 1993) did not have a way for clients to tell servers what kinds
of images they supported, thus the design dilemma that Marc faced.
A few hours later, Tony Johnson replied:
I have something very similar in Midas 2.0 (in use here at SLAC, and due for public release
any week now), except that all the names are different, and it has an extra argument
NAME="name". It has almost exactly the same functionality as your proposed IMG tag. e.g.,
<ICON name="NoEntry" href="http://note/foo/bar/NoEntry.xbm">
The idea of the name parameter was to allow the browser to have a set of “built in”
images. If the name matches a “built in” image it would use that instead of having to go
out and fetch the image. The name could also act as a hint for “line mode” browsers as
to what kind of a symbol to put in place of the image.
I don’t much care about the parameter or tag names, but it would be sensible if we used
the same things. I don’t much care for abbreviations, i.e., why not IMAGE= and SOURCE=. I
somewhat prefer ICON since it implies that the IMAGE should be smallish, but maybe
ICON is an overloaded word?
Midas was another early web browser, a contemporary of X Mosaic. It was cross-
platform; it ran on both Unix and VMS. “SLAC” refers to the Stanford Linear
Accelerator Center, now the SLAC National Accelerator Laboratory, which hosted the
A Long Digression into How Standards Are Made | 3