HTML Advanced tutorial 26 : HTTP Status Messages

When a browser requests a service from a web server, an error might occur. This kind of error is shown using Status Message. Below a list of HTTP status messages that might be returned from server. These Status Messages are categories into different tables based on their type of responses.

Information :

These types of HTTP Status Message starts with 1xx. Their details are below.

Message:	Description:
100 Continue	The server has received the request headers, and the client should proceed to send the request body
101 Switching Protocols	The requester has asked the server to switch protocols
103 Checkpoint	Used in the resumable requests proposal to resume aborted PUT or POST requests

Successful :

These types of HTTP Status Message starts with 2xx. Their details are below.

Message:	Description:
200 OK	The request is OK. This is the standard response for successful HTTP requests.
201 Created	The request has been fulfilled, and a new resource is created
202 Accepted	The request has been accepted for processing, but the processing has not been completed
203 Non-Authoritative Information	The request has been successfully processed, but is returning information that may be from another source
204 No Content	The request has been successfully processed, but is not returning any content
205 Reset Content	The request has been successfully processed, but is not returning any content, and requires that the requester reset the document view
206 Partial Content	The server is delivering only part of the resource due to a range header sent by the client

Redirection :

These types of HTTP Status Message starts with 3xx. Their details are below.

Message:	Description:
300 Multiple Choices	A link list. The user can select a link and go to that location. Maximum five addresses
301 Moved Permanently	The requested page has moved to a new URL
302 Found	The requested page has moved temporarily to a new URL
303 See Other	The requested page can be found under a different URL
304 Not Modified	Indicates the requested page has not been modified since last requested
306 Switch Proxy	No longer used
307 Temporary Redirect	The requested page has moved temporarily to a new URL
308 Resume Incomplete	Used in the resumable requests proposal to resume aborted PUT or POST requests

Client Error :

These types of HTTP Status Message starts with 4xx. Their details are below.

Message:	Description:
400 Bad Request	The request cannot be fulfilled due to bad syntax
401 Unauthorized	The request was a legal request, but the server is refusing to respond to it. For use when authentication is possible but has failed or not yet been provided
402 Payment Required	Reserved for future use
403 Forbidden	The request was a legal request, but the server is refusing to respond to it
404 Not Found	The requested page could not be found but may be available again in the future
405 Method Not Allowed	A request was made of a page using a request method not supported by that page
406 Not Acceptable	The server can only generate a response that is not accepted by the client
407 Proxy Authentication Required	The client must first authenticate itself with the proxy
408 Request Timeout	The server timed out waiting for the request
409 Conflict	The request could not be completed because of a conflict in the request
410 Gone	The requested page is no longer available
411 Length Required	The "Content-Length" is not defined. The server will not accept the request without it
412 Precondition Failed	The precondition given in the request evaluated to false by the server
413 Request Entity Too Large	The server will not accept the request, because the request entity is too large
414 Request-URI Too Long	The server will not accept the request, because the URL is too long. Occurs when you convert a POST request to a GET request with a long query information
415 Unsupported Media Type	The server will not accept the request, because the media type is not supported
416 Requested Range Not Satisfiable	The client has asked for a portion of the file, but the server cannot supply that portion
417 Expectation Failed	The server cannot meet the requirements of the Expect request-header field

Server Error :

These types of HTTP Status Message starts with 5xx. Their details are below.

Message:	Description:
500 Internal Server Error	A generic error message, given when no more specific message is suitable
501 Not Implemented	The server either does not recognize the request method, or it lacks the ability to fulfill the request
502 Bad Gateway	The server was acting as a gateway or proxy and received an invalid response from the upstream server
503 Service Unavailable	The server is currently unavailable (overloaded or down)
504 Gateway Timeout	The server was acting as a gateway or proxy and did not receive a timely response from the upstream server
505 HTTP Version Not Supported	The server does not support the HTTP protocol version used in the request
511 Network Authentication Required	The client needs to authenticate to gain network access

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HTML Advanced tutorial 25 : HTML URL Encoding

URL encoding converts characters into a format that can be transmitted over the Internet. Web browsers request pages from web servers by using a URL. The URL is the address of a web page, e.g http://www.yoursite.com.

URLs can only be sent over the Internet using the ASCII character-set. Since URLs often contain characters outside the ASCII set, the URL has to be converted into a valid ASCII format. URL encoding replaces non ASCII characters with a "%" followed by two hexadecimal digits. URLs cannot contain spaces. URL encoding normally replaces a space with a + sign.

URL Encoding Examples

Character            URL-encoding
€                           %80
£                           %A3
©                          %A9
®                          %AE
À                          %C0
Á                          %C1
                          %C2
à                          %C3
Ä                          %C4
Å                          %C5


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HTML Advanced tutorial 24 : HTML URL

A URL ( Uniform Resource Locator ) is another word for a web address. A URL can be composed of words,  or an Internet Protocol ( IP ) address. Most people enter the name of the website when surfing, because names are easier to remember than numbers.

When you click on a link in an HTML page, an underlying <a> tag points to an address on the world wide web. A URL is used to address a document (or other data) on the world wide web. A web address, like this, http://www.yoursite.com/html/index.html follows these syntax rules.

scheme://host.domain:port/path/filename


Below is the explanation of terms.

scheme -    defines the type of Internet service. The most common type is http
host -         defines the domain host (the default host for http is www)
domain -    defines the Internet domain name, like yoursite.com
:port -        defines the port number at the host (the default port number for http is 80)
path -        defines a path at the server (If omitted, the document must be stored at the root directory of the web site)
filename -   defines the name of a document/resource

Common URL Schemes
These are lists some common schemes.

http  =  HyperText Transfer Protocol :
Common web pages starts with http://. not encrypted

https  =  Secure HyperText Transfer Protocol:
Secure web pages. All information exchanged are encrypted

ftp  =  File Transfer Protocol:
For downloading or uploading files to a website. Useful for domain maintenance

file:
A file on your computer

HTML Advanced tutorial 25 : HTML URL Encoding  >>
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HTML Advanced tutorial 23 : HTML Entities

Some characters are reserved in HTML. It is not possible to use the less than (<) or greater than (>) signs in your text, because the browser will mix them with tags. To actually display reserved characters, we must use character entities in the HTML source code. A character entity may looks like this.
&entity_name;
OR
&#entity_number;
To display a less than sign we must write: &lt; or &#60; The advantage of using an entity name, instead of a number, is that the name is easier to remember. However, the disadvantage is that browsers may not support all entity names (the support for entity numbers is very good).

Non-breaking Space
A common character entity used in HTML is the non-breaking space (&nbsp;). Browsers will always truncate spaces in HTML pages. If you write 10 spaces in your text, the browser will remove 9 of them, before displaying the page. To add spaces to your text, you can use the &nbsp; character entity.

HTML Useful Character Entities

Entity names are case sensitive. Following is list of entity names with their description.

Result	Description	Entity Name	Entity Number
	non-breaking space	 	 
<	less than	&lt;	&#60;
>	greater than	&gt;	&#62;
&	ampersand	&amp;	&#38;
¢	cent	&cent;	&#162;
£	pound	&pound;	&#163;
¥	yen	&yen;	&#165;
€	euro	&euro;	&#8364;
§	section	&sect;	&#167;
©	copyright	&copy;	&#169;
®	registered trademark	&reg;	&#174;
™	trademark	&trade;	&#8482;

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HTML Advanced tutorial 22 : HTML Scripts

HTML script Element
The <script> tag is used to define a client-side script, such as a JavaScript and JQuery. The script element either contains scripting statements or it points to an external script file through the src attribute. The required type attribute specifies the MIME type of the script. Common uses for JavaScript are image manipulation, form validation, and dynamic changes of content.

For Example

<script type="text/javascript">
document.write("Hello!")
</script>

The script above writes Hello! to the HTML output.

HTML noscript Element
The <noscript> tag is used to provide an alternate content for users that have disabled scripts in their browser or have a browser that doesn’t support client-side scripting. The noscript element can contain all the elements that you can find inside the body element of a normal HTML page.

The content inside the noscript element will only be displayed if scripts are not supported, or are disabled in the user’s browser:

For example

<script type="text/javascript">
document.write("Hello!")
</script>
<noscript>This is not inside Script!</noscript>

HTML Script Tags

Tag                   Description
<script>            Defines a client-side script
<noscript>        Defines an alternate content for users that do not support client-side scripts

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