Comments on: 5a Missing schema double download

By: Petr Morávek

Petr Morávek — Tue, 21 Dec 2010 00:11:35 +0000

There is something really weird in how IE7 and IE8 (I have no idea what’s the status of IE9) handles protocol relative URLs. A while ago I stumbled on another bug related to them – page is reloaded after clicking on anchor link instead of simply jumping to the anchor – see the test page, if you’re interested:
http://php5.skauti-pardubice.cz/IE7-missing-scheme-bug.php

By: Eric Lawrence [MSFT]

Eric Lawrence [MSFT] — Thu, 02 Sep 2010 22:14:42 +0000

The reason that the problem appears intermittently isn’t related to Fiddler, but instead to timing.

Internal to Trident, the download queue has “de-duplication” logic to help ensure that we don’t download a single resource multiple times in parallel.

Until recently, that logic had a bug for certain resources (like CSS) wherein the schema-less URI would not be matched to the schema-specified URI and hence you’d end up with two parallel requests.

Once the resource is cached locally, the bug no longer repros because both requests just pull the cached local file.

By: Jon Galloway

Jon Galloway — Thu, 02 Sep 2010 19:45:39 +0000

This appears to be a problem with the latest IE9 preview.

http://www.flickr.com/photos/jongalloway/4951687517/

By: Klaus Johannes Rusch

Klaus Johannes Rusch — Thu, 04 Mar 2010 10:54:37 +0000

I have been unable to reproduce this behaviour using Internet Explorer 7.

Watching traffic with Fiddler shows no duplicate entries.

Requesting test pages using a direct connection without an intermediate proxy shows no duplicate entries in the logs either.

Maybe this affects certain versions of Internet Explorer only?

By: Steve Souders

Steve Souders — Mon, 01 Mar 2010 05:02:35 +0000

@Matthew: If the cache is empty, the stylesheet is fetched twice regardless of expiration headers.

@Miller: Perhaps Fiddler is affecting your tests. Fiddler (and other proxies) affect browser behavior. I’m using the latest HttpWatch.

By: Miller

Miller — Mon, 01 Mar 2010 03:08:44 +0000

Hi, I test many times on IE7 on Vista and use HTTPWatch 、Fiddler to capture, but can’t reproduce this problem, is it the same when capture with Fiddler? and could you tell what’s the version of your httpwatch?

By: Matthew Pennell

Matthew Pennell — Fri, 19 Feb 2010 16:05:07 +0000

Steve,

I would have assumed that the reason the protocol-less stylesheet on your test page is a 200 (non-cached) resource is that you have a querystring timestamp added to it.

If you remove those timestamps, are the resources cached? Specifically, is the second of the downloads of the protocol-less stylesheet loaded from cache.

By: Billy Hoffman

Billy Hoffman — Sat, 13 Feb 2010 19:39:57 +0000

ack! silly HTML filtering! Long story short, both using either [LINK] or @import to reference an external style sheet using a protocol relative URL results in IE7 and IE8 double downloading the file.

By: Billy Hoffman

Billy Hoffman — Sat, 13 Feb 2010 19:37:56 +0000

Steve,

Turns external CSS files referenced using protocol relative hyperlinks in @imports also results in a double download. Not that you should be using @import anyway, but both and @import result in double downloads.

By: Steve Souders

Steve Souders — Fri, 12 Feb 2010 04:53:45 +0000

Hi, Jason!

@tjschuck: Double download does not happen with root relative URLs. Only protocol relative URLs.