Metadata is information about data, and the meta tag in HTML is used to provide metadata or meta information about the HTML document.
This information is not displayed on the page and is instead used by search engines, browsers, and other tools to understand and interpret the content of the webpage.
The metadata is typically placed in the head of the HTML document, along with other elements such as the title tag, which specifies the title of the webpage, and links to external resources such as stylesheets and scripts.
The body tag is used to define the main content of the webpage, and it is placed after the head of the document.

HTML, Head, Title, Body

Explanation: The correct sequence of HTML tags to start a webpage is html, head, title, and body.

HyperText Markup Language

HTML is an acronym that stands for HyperText Markup Language, which is used for creating web pages and web applications.

HyperText simply means "Text within Text." A text has a link within it, is a hypertext. A markup language is a computer language that is used to apply layout and formatting conventions to a text document.

When the iframe> element is used, an iframe is analogous to a window that has been carved out of our page. 

In this, the attributes src, height, and width are basically used. 

The Src element defines the URL of the displayed page. 

Height and width give an iframe's height and width in pixels.

 In an unordered list in HTML, you can use the type attribute to specify the style of the bullet points. 
The three possible values for the type attribute are "disc", "circle", and "square".

The default value is "disc", which displays a solid bullet point. 
The value "circle" displays an empty bullet point, and the value "square" displays a square bullet point.

 You can create a checkbox in HTML using the <input> element with a type attribute set to "checkbox"

The type of list items is specified using the type property in conjunction with the <ol> element.

It is important to include the <!DOCTYPE> declaration at the beginning of your HTML document because it helps the browser to correctly render the content of the page. 
If the <!DOCTYPE> declaration is not present or is incorrect, the browser may not render the page correctly or may switch to a compatibility mode.

The background property must be specified in the HTML document's body> in order to apply a background picture to the whole content.