Source: Akamai.

What: Shares of Akamai Technologies (NASDAQ:AKAM) fell as much as 20% on Wednesday, following the release of solid third-quarter results with a side of disappointing guidance.

So what: The content delivery network (CDN) operator saw revenues rise 11% year over year to $551 million. On a constant-currency basis, sales increased by 15%. On the bottom line, adjusted earnings stayed flat at $0.62 per diluted share.

Analysts had expected earnings of $0.58 per share on sales of $550 million, so Akamai beat both of these oft-cited expectations.

Indeed, Akamai shares rose as much as 3% on this initial report. But Tuesday's after-market chart turned south with a vengeance during the earnings call, where management set up disappointing guidance targets for the fourth quarter.

Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Now what: In the fourth quarter, Akamai now expects to record revenues in the $567 million range. Adjusted earnings are seen landing near $0.62 per diluted share.

Your average Wall Street analyst currently expects fourth-quarter earnings of $0.65 per share on $597 million in top-line sales.

Akamai CEO Tom Leighton did his best to pad the guidance blow, explaining how the fourth quarter dips into the "external macroeconomic environment" to a unique degree. But that's not all:

Most notably, we expect a decline in revenue in Q4 in three of our largest U.S. media accounts, driven primarily by slowing traffic growth compared to our very strong Q4 of 2014. The impact is expected to be magnified by their do-it-yourself efforts, but most of the impact is from less traffic growth overall.

One might expect this horrific market environment to weigh on all major content delivery companies, but that isn't the case.

Level 3 Communications (NYSE:LVLT), which does a fair bit of CDN business besides its core networking operations, reported results on Wednesday morning. That report lifted Level 3 shares as much as 9% higher on Wednesday. Limelight Networks (NASDAQ:LLNW), which is the most direct rival in Akamai's focus markets, had no news of its own but rose 3% on the combination of Level 3 and Akamai news.

In short, Akamai's soft guidance makes it look like an underperformer in an otherwise healthy CDN sector.