X-UA-Compatible Meta Tag
Allows websites to work around rendering quirks in older versions of Internet Explorer.
The X-UA-Compatible meta tag is an old tag used by the Internet Explorer web browser to allow websites to work around rendering quirks in different versions of Internet Explorer. This meta tag is not used by any modern web browser.
This meta tag allows websites to choose which version of Internet Explorer is used to render the page. This could be useful if the webpage was designed to run on a certain version of IE, but would not run in newer versions, for some quirky reason. In fact, this was often called "Quirks Mode". It would almost always be better to fix the website so that it runs correctly in all versions of all web browser, but sometimes development time constraints made this difficult. With modern web browsers, this meta tag is no longer supported and it should not be used.
For historical reasons, here is an example of the meta tag and the possible values that it might contain.
<meta http-equiv="X-UA-Compatible" content="IE=edge">
For more information, please read the documentation from Microsoft.
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