One of my clients contacted me yesterday to tell me that there was a problem with reading their RSS feed in Safari (and only in Safari).
Over the next hour or so, I learned quite a bit about how the current version of Safari (3.2.1 as of this writing) handles RSS:
By default, Safari is configured to open up your default e-mail client to handle/read RSS feeds, resulting in a lot of head-scratching by your truly when I tried to navigate to the feed and ended up with a "Compose New Message" window in Thunderbird. While a lot of people do prefer the RSS-reading capabilities of their mail client over what the browser does with feeds, make that decision for the user is a questionable call on Apple's part, and some sort of alert/notice that this was the deal would have been nice.
...Those two issues are annoyances rather than bugs. The problem affecting my client's RSS feed, however, is a bug in regards to how Safari is transforming the RSS data before displaying it to the user.
Each news item in an RSS feed can contain a number of elements/nodes, two of which are the <link> and <guid> elements. The <link> element is meant to contain the URL where the reader can access the full text of the item. The <guid> element contains a string that uniquely identifies that RSS feed item within the feed (like a primary key in a database).
If the <guid> element contains the "isPermaLink" attribute and that attribute value is set to "true", then that indicates that the <guid> element also contains a URL (a permanent one) to the full text of the item (one that might be different from the URL in the <link> element), and an RSS client could legitimately used the URL in the <guid> as the link to the story instead.
What I discovered, though, was that Safari was creating the hyperlink for each news item by combining the value of the <link> element in the <channel> node of the RSS feed with the value of the <guid> element of each item (which was simply a unique numeric value), even though the <guid> elements did NOT contain the "isPermaLink" parameter. So instead of using the value of the <link> element of each item as per the RSS specs, Safari ended up creating non-existent URLs.
The solution, of course, was simple: I just put the URL for each news item in the <guid> element as well as the <link> element. Point is, I shouldn't have had to.
Once I applied the solution, I did some searching to find out if this is a known problem that was being worked on. I found one mention of it in a generic tech support forum post published in 2008, so it looks like the problem has existed for awhile but hasn't gotten much attention (probably because most people read RSS feeds through actual RSS clients). I used Safari's built-in bug report mechanism to report it to Apple, but I don't hold out much hope for that having an impact.
Still, I thought it worth a post, on the off-chance this information might help someone else.