For companies that sell physical products online, SEO isn’t just nice to have–it’s essential to the success of their business. But online retailers of all sizes face the same problem: What do you do with a product page when that product is no longer available? According to Matt Cutts, the head of Google’s Webspam team, the answer depends on a few factors, including the number of product pages, your company resources, and the nature of your business.

Small online retailers

If you are a small online retailer, you need to get the most out of every visitor to your website. While this is true of all e-commerce sites, it is especially important for retailers that are not a well-known brand. So if a product goes out of stock, it’s often a good idea to modify the product page. The updated product page can inform the shopper that the item they are looking for is out of stock. In addition, providing recommendations on the same page for similar products that are in stock is very smart. This strategy can salvage some sales out of visitors who otherwise would get discouraged and leave your company website empty-handed.

Mid-sized online retailers

If you are a mid-sized retailer with hundreds of product pages, Cutts recommends putting up a 404 page if you don’t want to invest in helping those customers find another product in your inventory. From Google’s perspective, a 404 page is optimal because it can be easily ignored by Google’s search algorithm as it tries to deliver the most relevant results to shoppers. Therefore, only include an out-of-stock page if you plan to help the user find what they are looking for or offer alternatives.

Large online retailers

Finally, if your online business is selling an enormous amount of goods, you might need a different strategy for managing defunct product pages. If you know that a certain product will be out of stock at a certain time, you can apply an unavailable_after meta tag to the product page:

unavailable_after: [RFC-850 date/time]

This tag tells Google to stop indexing the product page after the date you specify. It will cease to show up in Google search results, which is a good thing because that helps your website avoid any SEO penalties. This tactic is particularly useful for deal-of-the-day sites like Woot and user-based marketplaces like eBay or Craigslist.

Every online retailer is unique, and their SEO strategies should reflect that. Using the advice above, you can assess the size, goals, and resources of your own online retail business to determine how to deal with obsolete product pages.