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Stands for "Cascading Style Sheet." Cascading style sheets are used to format the layout of Web pages. They can be used to define text styles, table sizes, and other aspects of Web pages that previously could only be defined in a page's HTML.

Defination- CODE
1) In programming, code (noun) is a term used for both the statements written in a particular programming language - the source code , and a term for the source code after it has been processed by a compiler and made ready to run in the computer - the object code .
To code (verb) is to write programming statements - that is, to write the source code for a program.

2) In cryptography, code has both a specific technical meaning and a general meaning. In the technical sense, code is the substitution of one word or phrase by another word, number, or symbol for the purpose of concealing the original word or phrase. Basically, it's substitution at the word or phrase level. In industry, a developing product is sometimes given a code name to conceal its probable marketing name. Historically, military operations have often had a code name while in the preparation stage. In World War Two, Germany's invasion of the Soviet Union was given the code name of Barbarossa. Code in this sense is sometimes confused with a cipher , which is substitution of symbols at the letter level. Modern cryptography is much more concerned with ciphers than with code in its limited technical meaning.

Code is often used generally to mean any kind of concealed writing, including ciphers. "Breaking the code" usually means the discovery of a way to read one or a series of encrypted messages without being given the key to decrypt them.

Defination- HTML
HTML (Hypertext Markup Language)  is the language used to create webpages. "Hypertext" refers to the hyperlinks that an HTML page may contain. "Markup language" refers to the way tags are used to define the page layout and elements within the page.

The first line defines what type of contents the document contains. "<!doctype html>" means the page is written in HTML5. Properly formatted HTML pages should include <html>, <head>, and <body> tags, which are all included in the example above. The page title, metadata, and links to referenced files are placed between the <head> tags. The actual contents of the page go between the <body> tags.

The web has gone through many changes over the past few decades, but HTML has always been the fundamental language used to develop webpages. Interestingly, while websites have become more advanced and interactive, HTML has actually gotten simpler. If you compare the source of an HTML5 page with a similar page written in HTML 4.01 or XHTML 1.0, the HTML5 page would probably contain less code. This is because modern HTML relies on cascading style sheets or JavaScript to format nearly all the elements within a page.

NOTE: Many dynamic websites generate webpages on-the-fly, using a server-side scripting language like PHP or ASP. However, even dynamic pages must be formatted using HTML. Therefore, scripting languages often generate the HTML that is sent to your web browser.
Below is an example of HTML used to define a basic webpage with a title and a single paragraph of text.

<!doctype html>
<p>This is an example of a paragraph in HTML.</p>

JavaScript is a programming language commonly used in web development. It was originally developed by Netscape as a means to add dynamic and interactive elements to websites. While JavaScript is influenced by Java, the syntax is more similar to C and is based on ECMAScript, a scripting language developed by Sun Microsystems.

JavaScript is a client-side scripting language, which means the source code is processed by the client's web browser rather than on the web server. This means JavaScript functions can run after a webpage has loaded without communicating with the server. For example, a JavaScript function may check a web form before it is submitted to make sure all the required fields have been filled out. The JavaScript code can produce an error message before any information is actually transmitted to the server.

Like server-side scripting languages, such as PHP and ASP, JavaScript code can be inserted anywhere within the HTML of a webpage. However, only the output of server-side code is displayed in the HTML, while JavaScript code remains fully visible in the source of the webpage. It can also be referenced in a separate .JS file, which may also be viewed in a browser.

Below is an example of a basic JavaScript function that adds two numbers. The function is called with the parameters 7 and 11. If the code below were included in the HTML of a webpage, it would display the text "18" in an alert box.

function sum(a,b)
return a + b;
var total = sum(7,11);

JavaScript functions can be called within <script> tags or when specific events take place. Examples include onClick, onMouseDown, onMouseUp, onKeyDown, onKeyUp, onFocus, onBlur, onSubmit, and many others. While standard JavaScript is still used for performing basic client-side functions, many web developers now prefer to use JavaScript libraries like jQuery to add more advanced dynamic elements to websites.