What is a meta tag? What are the common meta tags?

　　What Are Meta Tags?

　　Meta tags are a type of HTML tag used between the head tags of a web page. They mainly include keyword tags and description tags, and these two are also the most commonly used today.

　　Meta tags appear in the head tag of a web page's HTML source code. Different meta tags serve different purposes, and their only difference from other HTML code is that they are not displayed directly on the monitor. Meta tags have various effects on a web page: some introduce the version of the page, and some introduce the author who wrote it.

　　In the actual practice of building websites, very few meta tags are genuinely used, but since the SEO industry rose, all kinds of neglected tags have been put back to use. For example, sometimes a robots.txt file cannot handle some special situations, so in-page robots tags are used instead to guide the direction in which spiders crawl.

　　What Are the Common Meta Tags?

　　abstract: similar to the description meta tag, it can be used to describe a web page.

　　unavailable_afer: an upcoming new web page tag. It stops Google from crawling pages bearing this marker after a certain time, which can relieve a website's server load.

　　distribution: rarely used in web pages. If a page is only meant for internal distribution, then the Robots.txt file or the robots meta tag should be used to prohibit indexing.

　　copyright: similar to the author meta tag; it is usually used to protect original work

　　classification: think about how the keywords meta tag is exploited by spam websites — this one is the same; I have never seen such a careless meta tag.

　　keywords: specifies the particular positioning words for the page; use it to place 2~3 keywords that can describe the page.

　　author: defines the author of the web page, usually used to protect original copyright.

　　Cache-control: can control the caching situation of a web page. In the past this tag was used to stop users from seeing outdated content on a website. Note: if you don't want certain content to be snapshotted by search engines, you should use the robots meta tag to achieve that.

　　description: the description tag of a web page; use it to specify the description content of the page to search engines.

　　designer: like author and copyright, it is used to protect original work.

　　revisit-afer: adjusts the spider's visit frequency. Its role is to tell the spider to crawl according to a set visit frequency, which can greatly reduce the frequency of repeatedly crawling pages, such as login pages, registration pages, etc.

　　robots: a tool for issuing orders to spiders. It can be used to prohibit the crawling of some noise files.

　　tite: the unique title tag of a web page. It can intuitively tell users the nature of the content discussed on this page

　　Googlebot: it is Google's web crawling robot; for a web page to be indexed, it must first be crawled by Googlebot.

　　expires: specifies that spiders should no longer crawl after a certain period of time.

　　Content-language: used to define the language code used by the page. It specifies the language encoding for spiders

　　Content-type: specifies a string describing the page type; it can be used to specify the character set for the page, ensuring that you specify the same character set on all pages.

　　mobot:msn: a client tool for the robot control service. Through this mobot you can remotely control the machine running this program.

　　That is all of "What Are Meta Tags? What Are the Common Meta Tags?", provided for webmaster friends to interact, exchange and learn together. SEO Optimization is a process that requires persistence, and I hope we can all make progress together.