Parsing relative URLs

carlbernardi · Jun 1, 2008

Hi,

While parsing relative URL segments "../" to hierarchical segments of
the absolute URL , I notice that the <a> tag and the <link> tag do
this differently. Take the following absolute and relative URLs:

absolute URL: http://www.a.com/a/b
relative URL: ../../b/c.css

The <a> tag resolves this to:

http://www.a.com/b/c.css

However the <link> tag resolves this to:

http://www.a.com/a/b/c.css

It appears that all other forms of resolving URLs are equal between
both tags however, I have been trying to find the RFC specification on
this but have had no luck. This document http://www.ietf.org/rfc/rfc2396.txt
does not contain any information regarding the <link> tag.

Is anyone here familiar with this or know where I could obtain more
information.

Thanks,

Bandito

http://www.gaihosa.com

Lars Eighner · Jun 1, 2008

In our last episode,

the said:
Hi,

While parsing relative URL segments "../" to hierarchical segments of
the absolute URL , I notice that the <a> tag and the <link> tag do
this differently. Take the following absolute and relative URLs:

absolute URL: http://www.a.com/a/b
relative URL: ../../b/c.css

But this is nonsense. It is looking for the parent of the root,
but of course there cannot be one.

The <a> tag resolves this to:

However the <link> tag resolves this to:

http://www.a.com/a/b/c.css

In other words, some browser or another, presented with an absurdity, has
inconsistent error handling. Well, obviously, other than writing to the
authors of the browser about that, the solution would be not to write
relative URLs that are absurd.

It appears that all other forms of resolving URLs are equal between
both tags however, I have been trying to find the RFC specification on
this but have had no luck. This document http://www.ietf.org/rfc/rfc2396.txt
does not contain any information regarding the <link> tag.

I don't think you will find many specs that deal with error recovery. There
are so many possible errors that the point of defining the right way would
be lost in all the stuff about what to do when people do things the wrong
way.

Is anyone here familiar with this or know where I could obtain more
information.

-
Lars Eighner <http://larseighner.com/> (e-mail address removed)
Countdown: 232 days to go.

Harlan Messinger · Jun 1, 2008

Hi,

While parsing relative URL segments "../" to hierarchical segments of
the absolute URL , I notice that the <a> tag and the <link> tag do
this differently. Take the following absolute and relative URLs:

absolute URL: http://www.a.com/a/b
relative URL: ../../b/c.css

The <a> tag resolves this to:

http://www.a.com/b/c.css

Not in my test.

However the <link> tag resolves this to:

http://www.a.com/a/b/c.css

File /a/b/c.css:

body { color: red; }

File /b/c.css:

body { color: green; }

File /a/b/x.html:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>Relative URLs: Link vs. A</title>
<link rel="stylesheet" type="text/css" href="../../b/c.css">
</head>

<body>
If the LINK tag resolves the relative URL
to http://localhost/b/c.css, this will be green.
If it resolves it to http://localhost/a/b/c.css,
this will be red.
<a href="../../b/c.css">Click here</a>
</body>
</html>

In both Internet Explorer and Firefox, the page's text appears in green,
and the link leads to the file that reads

body { color: green; }

In other words, both the LINK and the A tags point--correctly--to
/b/c.css. Therefore, I think you made a mistake somewhere in your
experiment.

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Parsing relative URLs

carlbernardi

Lars Eighner

Harlan Messinger

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