A round-up of the companies, deals, and trends that made headlines.

Every day, the Fortune staff spends hours poring over tech stories, posts, and reviews from all over the Web to keep tabs on the companies that matter. We've assembled the day's most newsworthy bits below.

• Dozens of online stores -- including Toys 'R' Us, Barnes & Noble (BKS), and Radio Shack (RSH) -- have teamed up to launch a counter-offensive to Yahoo's Amazon Prime service, offering a cooperative loyalty program called ShopRunner. The service offers free 2-day shipping and free returns. (The Wall Street Journal)
• According to StatCounter, Internet Explorer, still the world's most widely used web browser, dropped below a 50% share of the market, down from nearly 60% a year ago. (Google 24/7)
• GigaOm has a nice roundup of startup post-mortems, including comments from Wesabe co-founder Marc Hedlund, whose personal savings site folded thanks to Mint.com's success, and Standout Jobs co-founder Ben Yoskovitz, who sold the startup back in May and has moved on to a seed fun/incubator called Year One Labs. (GigaOm)
• Foursquare attributes its recent 11-hour crash, the longest downtime in the social network's history, to an overload of what they call "shards," packets of their database where they store check-ins. (Mashable)
• As part of its top-secret event tomorrow, Facebook may unveil a redesign. (TechCrunch) More