When I view the source html of pages on some websites, in addition to the usual meta tags I’ve noticed that some are crammed full of other meta tags like ‘robots’, ‘revisit-after’, ‘author’, ‘rating’, etc. Should I be using all these on my pages?
In a word, no. Unless the meta tag you’re thinking of using serves some purpose, don’t use it. The most common mistake is to use the ‘robots’ meta tag to instruct the search engine spiders to ‘index, follow’. This is of course what the search engine spider is going to do anyway, making the use of the tag in this case completely pointless. It should actually only be used when instructing spiders not to do something. e.g. noindex, nofollow.
The ‘revisit-after’ tag is also pointless, as the search engine spiders follow entirely their own timetable.
Other commonly used meta tags, including any that you might create yourself, should only be used if they serve some purpose. In truth, it’s rare that they serve any real purpose, and they don’t improve anything from an SEO perspective. Actually, most pages benefit from having the superfluous meta tags removed, and reducing the footprint of the page.