This is an alert to all sellers using Gmail that rely on e-mail to notify them of sales, INRs, returns, offers, buyer messages, payment notices, or anything else selling-related that they should log in to each of their eBay accounts directly to make sure they're not missing anything.
This is something sellers should always do anyway, but for those that don't - this is your heads up. For the last 2 hours or so Gmail has been down for most users and Google is estimating a resolution about 40 minutes from now. (status updates)