Keynote Systems’ July 2011 News and Portal Index, an exclusive to Wireless Week, found that most mobile websites saw in increase in speed and performance, while third-party content had an adverse impact on how a page loaded.

Average page load time of the 21 sites included in the Index was 14.17 seconds, an improvement over June’s average load time of 15.34 seconds. Success rate was down slightly to 96.99 percent from 97.49 percent in June. Facebook had the fastest page load time of 4.29 seconds, and MSNBC had the highest success rate of 98.72 percent.

Fully 14 of the 21 mobile websites in the index showed positive improvement in page load time from June to July. AOL showed the largest improvement with 4.4 seconds to 21.99 seconds and USA Today improved by 2.87 seconds to 22.25 seconds. Although they enjoyed the largest improvement, they are still behind the leaders in terms of page load time when compared to other News and Portal sites.

On the success rate side, there were more sites with lower success rates than higher. Six sites had an increase in success rate. ABC news had the largest success rate increase of 98.09 percent, while LinkedIn had the second largest increase and went up to 96.45 percent availability.

The most available site still wasn’t accessible 1.28 percent of the time — the equivalent of being out of business for five days over the course of a year.  A website’s success rate at the lower end (91.5 percent) would essentially be offline for a month.

Fox News’ success rate dropped by 6.41 percentage points compared to June. Upon closer examination of the monitoring data, Keynote found that the site was actually up, but a third party JavaScript object became inaccessible for two days. During this time, the mobile browser timed out when trying to download this object. Fortunately, Fox News removed this object from the page and the page resumed loading normally again.

Keynote says this is a classic example of why it is so important to monitor third-party content because when something is wrong, it can severely affect the user experience. On a positive note, Fox News had a strong improvement in page load time, increasing from 15.1 seconds to 12.71 seconds.

Despite the summer heat, The Weather Channel joined Facebook as the only two sites placing in the top five for both page load time and availability. It remains to be seen if they can keep up with the social media giant’s streak of being ranked in the top five for performance for five consecutive months.

The July leaders for page load time are Facebook, Google, Bing, Google News and The Weather Channel. The top four sites with highest success rate are the same in July as it was in June: MSNBC, The Weather Channel, Yahoo, and Facebook. CNN moved up to have the fifth highest success rate in July.

Keynote repeatedly tests the sites in the index hourly and around the clock from four locations over the leading four U.S. wireless networks, emulating the browsers of four different devices:  the iPhone 4 on AT&T, the HTC Evo (Android operating system) on Sprint, the Motorola Droid X (Android) on Verizon Wireless and the BlackBerry Curve on T-Mobile USA. Data is collected from San Francisco, New York, Dallas and Chicago and then aggregated to provide an overall monthly average in terms of both speed and reliability.