If your organization’s Web site isn’t up to speed, you could be losing donors and other supporters. But a free online tool, Google’s Page Speed, can help offer a quick analysis of the code on your site to determine whether it is loading as quickly as it can and offers recommendations for changes that can add zip to a sluggish site.

Those recommendations also come with a Page Speed score designed to show how much a site can improve. The score doesn’t measure the actual time it takes for a site to load on a computer screen, because that is influenced by the size of a page in bytes, server hardware, and other factors. But it does help gauge whether a site is performing as well as it can.

Sites that need significant improvements score below 50 out of 100. If a site is more modern, with best practices in place, it will probably score in the 80s or 90s.

The top 25 charities included in the Chronicle’s 2011 Philanthropy 400 scored a median of 73 out of 100 for their home pages when viewed on computers and 65 out of 100 when viewed on a mobile device, according to a Chronicle review of those sites.

The Boys & Girls Clubs of America scored second among the 25 largest organizations, with an 86 on a computer and 82 on mobile. Those high scores may result from the charity’s new emphasis on mobile devices, says Karl Kaiser, senior director of creative services and interactive communications at the organization.

“We’ve noticed a steady increase in visits to our site via mobile devices in the past six months, so we’ve been testing the latest in CSS 3 and HTML 5 [code] to maximize site experiences across all browsers and platforms," Mr. Kaiser says. "It appears to be making a difference."

One way the organization increases speed is to load all the repeated elements—navigation, backgrounds, logos, etc.—when visitors first come to the site. Those files are then saved on the visitors' computers. That way, the elements are downloaded just once and each subsequent page will load only new content.

It's a simple strategy, Mr. Kaiser says, but groups often ignore it as their sites get more complex.

"Many developers overlook components and ultimately unnecessary page elements start piling up and slowing down the page load times on each refresh," Mr. Kaiser says.

At the other end of the list, the American Red Cross scored second to last among the top 25 charities, recording only 46 of 100 points on a computer, and 52 of 100 on a mobile device. The organization's site is being redesigned, and its new site is expected to debut soon, says Anne Marie Borrego, a spokeswoman.

Here's how all 25 sites performed in the Page Speed tests:

Amnesty International USA, which isn't among the top 25 on the Philanthropy 400, scored 93 points on a computer and 91 points for mobile. Other Web-savvy charities with newer sites also scored well: Charity: Water scored 87 on a computer and 82 on mobile, AND DonorsChoose.org scored 83 on a computer and 90 on mobile.

The Nonprofit Technology Network scored 59 on a computer and 58 on mobile, lower than all but four of the 25 charities from the Philanthropy 400 on a computer, and lower than all but nine on mobile.

All nonprofits can take comfort in knowing that almost no group is perfect: Google scored a 99 on both computers and mobile devices, and it created the scoring system.

How does your nonprofit's page Web site compare?

Send an e-mail to Cody Switzer.