The browser market share for Internet Explorer and Firefox sees a dip on the weekend on major retail websites, while Mobile Safari is the biggest gainer, an analysis of online shoppers’ browser preferences shows.

IE’s average market share drops from 40.65 percent during the week to 35.82 percent on the weekend, a relative decrease of nearly 12 percent, and Firefox’s market share sees a relative decrease of about 3.5 percent, from 16.38 percent to 15.81 percent, suggesting that many workers who use IE and Firefox at the office prefer to use other browsers when at home.

Meanwhile, Mobile Safari, which is available on the iPhone and iPad, sees a more than 30 percent relative gain, climbing from an average market share of 12.81 percent on weekdays to 16.75 percent on the weekend.

The analysis is based on browser data collected by Monetate from nearly a quarter-billion online shopping sessions on more than 100 major retail sites during a 30-day period ending May 15, 2012.

Chrome (the most popular browser after Internet Explorer), Safari and Opera each saw smaller bumps on the weekend.

Current vs. outdated versions

Although Internet Explorer’s total market share drops on the weekends, IE actually sees gains when outdated versions (IE 8 and below) are excluded. The average market share for IE9 rises from 18.34 percent during the week to 20.45 percent on the weekend, a relative gain of about 11.5 percent.

Similarly, the average market share of up-to-date Firefox versions (those above version 10) sees not a loss but a very slight gain during the weekend.

Firefox 3.6 is third most popular version

In early 2011, Firefox switched to a rapid-release development model to mirror Chrome’s, in which a new version of the browser is released every few weeks. (To give you an idea of the difference: the release dates of Firefox 3 and Firefox 4 were more than two and a half years apart. But the release dates of Firefox 4 and Firefox 11 were less than a year apart.)

The final major release before the switch to the accelerated development schedule was Firefox 3.6, and it appears that many of those users remain holdouts, either because they never made the decision to upgrade or because there were impediments to upgrading (such as instructions from a wary IT department to maintain their current version).

As a result, Firefox 3.6 remains the third most popular version of the browser, based on Monetate’s traffic data, topped only by Firefox 11 and Firefox 12, the most recent releases. Indeed, Firefox 3.6′s share of the market comes close to surpassing the combined market share of all the intermediate releases (4 through 10).

Workplaces less secure than home

Along with new features and enhancements to the user interface, most browser version releases also include bug fixes and security patches, so a simple way to make your browsing more secure is to update your browser to the latest available version.

But an analysis of Monetate’s traffic data shows that online shoppers who use Firefox or Internet Explorer on the weekends are more likely to use an up-to-date version than those who use them during the week, suggesting that office workers are better protected at home than they are at their cubicles.

About 30 percent of online shoppers using Firefox during the week were using an out-of-date version (10 or below), compared with only about 27 percent during the weekend. The difference was starker with IE. About 55 percent were using an out-of-date version (8 or below) during the week, compared with only about 43 percent during the weekend.

To be sure, frequent browser version upgrades cause more headaches for business users and IT departments than personal users, since corporate networks need to have confidence that an upgrade isn’t going to break mission-critical web applications. But the security stakes tend to be higher for business users, which makes it all the more surprising that many continue to rely on older browsers.

Fortunately, two trends offer hope to those of us who have to support these out-of-date browsers: shorter development cycles (even old stuck-in-the-mud Internet Explorer is moving in that direction) and shorter product lifecycles (the period for which any given version of a browser is actively supported). Sooner or later, no matter which browser they rely on, corporate IT departments are going to have to adjust to browsers as software products that continually evolve, and when they make that adjustment, we expect to see the market share of out-of-date browser versions decline precipitously.