November 12th, 2006 | Published in Google Merchant
By Clint Guerrero, Google Base Support
I see a variant of this question nearly every day of the week, and it's one that I'm eager to answer. After all, an image can describe an item much better than a thousand words.
To help you make sure your images appear the first time around, here are some of the most common issues:
HTML "images:" Faulty image links are the most common cause of an image not appearing. To successfully process an image, its associated image_link must link to an image rather than web'sge. Typically an image_link should end in the extension of one of our supported image file types: .gif, .jpg (or .jpeg), .png, .bmp, or .tif.
Re-directs: An image_link should also link directly to an image. If the image_link redirects to another URL of the image we won't be able to grab a copy of your image to add to search results. The URL in your bulk upload must match the URL that displays the image exactly.
HTTP headers: Every time information is passed through the "tubes of the Internet," it's preceded by a short description generally called a header. If the header info for an image isn't what is expected, the image processor is unable to cache a copy of your image. Typically, headers may only be an issue for images that are dynamically generated. If you don't know if your images are dynamically generated, this isn't likely to be the problem.
Two header fields that must be passed are "content-type" and "content-length." Content-type describes the file type you're sending. Two common values for images are "image/gif" and "image/jpeg." Content-length lets us know the file size for an image. A header field that shouldn't be passed is "cache-control." If you choose to add header fields, please make sure that they are appropriate for the image.
Image size: We will accept images up to 4MB or 8 million pixels in total size, but it's best to include images of 400x400 pixels or a bit larger. This image size allows us to include a non-distorted image in search results and reduces the possibility of overwhelming your server by requesting your super-sized images.
Robots.txt: A robots.txt file provides restrictions to search engine robots ("bots") that crawl the web. If it's set to prevent access to a certain directory, such as /images, we will be unable to visit that directory to retrieve your images.
This should cover the vast majority of problems you'll face, but if you're still running into issues, shoot us an email and we'll take a look.