Today’s study notes HTTP, HTML, CSS_html/css_WEB-ITnose

I started learning JavaWeb these days, and it was quite interesting. First I introduced HTML (Hyper Text Markup Language), CSS (Cascading Style Sheets), and HTTP protocol (Hyper Text Transfer). Protocol Hypertext Transfer Protocol), I mainly record the HTTP protocol, this part is still very important.

First point: HTTP protocol is an application layer protocol. When you browse the web, the browser and the server will send and receive data on the Internet through Http. HTTP is a request-based /Responsive mode, stateless protocol

In the Http1.1 version, a continuous link mechanism is provided. This is the difference from Http1.0.

Second point: HTTP URL format: http://host[:port][abs_path]

Where:

http Indicates that network resources are to be located through the HTTP protocol;

Host indicates a legal Internet host domain name or IP address (expressed in dotted decimal format);

Port is used to specify a port number, with The server host of the requested resource listens to the TCP connection on this port;

abs_path specifies the URI (Uniform Resource Identifier, Uniform Resource Identifier) ​​of the requested resource.

URL is a special type of URI that contains enough information to find a resource.

The third point: HTTP is divided into requests and responses

HTTP request: request line, message header, request body;

HTTP Request format: -Method Request-URI HTTP-Version CRLF

Method request methods mainly include GET, POST, HEAD... When we access the web page by directly entering the URL in the browser's address bar At that time, the browser used the GET method to obtain resources from the server, and the POST method was used to send a request to the server, requiring the server to accept the data attached to the request. The POST method is most commonly used when submitting forms.

The difference between get and post methods:

1): The results presented in the browser address bar are different, the appearance

2): The real reason is to send the message to the server The request format is different

3): get request format:

GET/test/LoginServet?username=hello&password=world HTTP/1.1

4): post Request format: POST/test/LoginServlet HTTP/1.1

HTTP response: status line, message header, response body

HTTP response format: -HTTP- Version Status-Code Reason-Phrase CRLF

The response code consists of three digits:

-1xx: Indication information--indicates that the request has been received and continues to be processed

-2xx :Success--Indicates that the request has been successfully received, understood, and accepted

-3xx: Redirect--Further operations must be performed to complete the request

-4xx: Client error-- The request has a syntax error or the request cannot be implemented

-5xx: Server-side error - the server failed to implement a legal request

As for CSS, I mainly record how to insert the style sheet:

Method 1: External style sheet

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mystyle.css:

-hr{color:sienna}

-p{margin-left:20px}

-body{background-image:url("images/back40.gif")}

Method 2: Embedded style sheet

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Method 3: Line style

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This is a paragraph

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