Canonical Elements
If two pages on your website feature similar content, search engines may have trouble determining which page is most important.  Canonical elements (aka canonical tags) help search engines understand which page is most important.
Canonical tags are included in the page HTML. That tag includes a link pointing to your preferred website content. Search engines use that information to help them determine the best URL for their index. This tag also helps prevent duplicate content issues.
In Good Gallery, you can include the same photo in more than one gallery. If you choose to display photos in more than one gallery, you would normally have a duplicate content issue. However, our software can recognizes this issue and automatically create a canonical entry that points to your most important photo based on your menu hierarchy.
Simply said, canonical tags help search engines understand the relative importance of similar content on your website.
Self-Referential Canonicals
Most pages of your website won't include duplicate content. But search engines can never be sure that duplicate content might exist. For that reason, Good Gallery includes self-referencing canonical link tags. In other words, our software includes self-referencing canonical link tags on most pages.
There are several benefits to self-referencing canonical link tags.
First, Google recommends using self-referencing canonicals. Including that information makes it explicitly clear which URL should be used as the official content. Sometimes external links to your pages may include special parameters, upper or lowercase letters, and www or non-www subdomains. Using self-referencing canonicals prevents these variants from becoming issues for you.
Second, self-referencing canonicals help prevent lazy screen scrapers from taking a page of HTML code from your website and using it elsewhere. When that’s done, canonical information is also included and any benefit the screen scraping site owner might have is negated since the canonical reference would point back to your site.