A reminder about what meta tags are?
Meta tags contain metadata. Meta data is information about data.
The meta tag provides metadata about the HTML document that the internet browser is viewing. Metadata is not displayed on the page itself, but will be machine parsable.
Meta elements are used to specify page description, keywords, author of the document, last modified and other metadata.
The metadata can be used by browsers. Metadata tells a browser how to display content or reload page, shows search engines a list of keywords, or can be used by other web services
Which meta tags are proper and HTML valid?
According to the W3C, the keywords, description, author, robots, and refresh meta tags are HTML and HTML 5 valid. HTML 5 meta tags must be closed unlike with HTML 4.0.
See the following examples
<meta name="keywords" content=" "/> <meta name="description" content="" /> <meta name="author" content=" " /> <meta name="robots" content="index,follow" /> <meta http-equiv="refresh" content=" "/> <meta charset="UTF-8"/>
Other valid meta tags include view port which is used for different devices including mobiles.
<meta name="viewport" content" "/>
What meta tags are invalid?
It is strongly encouraged that code writer valid their HTML code frequently and good validator programs such as the W3C validator will check what meta tags are either redundant or invalid.
Here are just some of the many meta tags which appear as invalid in a HTML validator.
<meta name="web_author" content=" " /> <;meta name="copyright" content=" " /> <meta name="language" content=" " /> <meta name="reply-to" content=" " > <meta http-equiv="pragma" content=" " />
Many of these meta tags are not needed at all and some are just a waste of characters.
Note that the meta tags such as "web_author" and "copyright" can be removed from your list a meta tags you can add a author’s name and copyright information as simple text in the footer of a web page.
The language meta tag has its own attribute in HTML 5.