META tags are still relatively important for on-page search engine optimization. Though sites may be indexed without them, websites that fail to include them may find that their ranking in the SERPs and consequently their organic search traffic suffers as a result. The three most important META tags for SEO purposes are the title, description and keywords tags.
A unique title tag is one of the two most important META tags on a page. It should contain branding elements for the website, keywords and should also entice visitors to click on the link to visit the page. Most search engines will only read and display the first 70 characters included in the title tag. The characters at the beginning of the title are believed to be weighted more heavily by most major search engines. Many sites put the keywords and description at the beginning of the title and the branding at the end for this reason.
A unique description tag should be no more than 150 characters to ensure that the full description is displayed in the SERPs across all search engines without being truncated. Keywords may be included in the description but should not detract from its readability. The description should read like ad copy and entice visitors to click through to the content. It is important to note that the description and title tags are the only significant information displayed in the SERPs about a website. Visitors will make the initial decision to click through or move on to another page based almost solely on the information contained within these two tags.
The keywords META tag is obsolete for all practical purposes. Search engines stopped using it years ago primarily because it was an unreliable way to judge what the content of a page was about. Some smaller search engines continue to use it and many content sites use the tags internally to index content for proprietary search functions. It certainly will not hurt a site’s ranking in the search engine results to include the keywords tag even if it does nothing positive for the ranking. If the tag is used, ensure that the included keywords are appropriate for the content on the page.
There are dozens of other META tags that can be included on a page. Most other tags are either obsolete or used for proprietary purposes only. These other tags often are of no SEO value to websites and only place an additional burden on the web development team. The title, description and keywords tags are the only META tags that most websites need to bother with for SEO purposes.