PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.
QQ Mail provider
The DOCTYPE is a required preamble for HTML5 websites.
Allows a website to define how a page is rendered in Internet Explorer 8, allowing a website to decide to use IE7 style rendering over IE8 rendering.
The http-equiv attribute provides an HTTP header for the information/value of the content attribute.
The http-equiv attribute can be used to simulate an HTTP response header.