Argh; MSIE and bandwidth

It appears that if you set the Cache settings in IE to “Automatically” or “Every visit to the page”, then every time you visit a page at IE fetches all page objects (page, CSS, favicon, embedded images). For some of them, it is sending the If-Modified-Since: header (I see 304 responses for the blog CSS, for example), but it does not seem to be sending If-Modified-Since: for the banner JPEGs. This means that MSIE visitors download the banners several times in a row as they browse the site. This not only wastes my bandwidth, but it also interferes with their experience, since they have to wait for the banner to download on every page visit.

I’ve noticed IE doing this before on the client side with image intense applications (like MovableType :-), but I hadn’t investigated until recently, when a small increase in visitors to my blog site _doubled_ the bandwidth used…

Is this a known IE bug? Is there anything I can do on the server side to work around it? The investigation continues…

posted at 8:44 am on Saturday, August 21, 2004 in Rants, Site News | Comments (2)


  1. Reid says:

    You could conditionally use a low-res substitute for IE users..

  2. Harald says:

    An excellent suggestion, and trivial to implement. Since WordPress already shoves a bunch of rewrite rules into a .htaccess file, it is trivial to add another one to conditionally rewrite the .jpg URLs for MSIE users. I’ve compressed the JPEGs to about 20% of their original size. The quality suffers, but less than I expected it would…

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