Tuesday, January 18, 2011

web page

Web page
A web page or webpage is a resource of information on the World Wide Web, viewed through a web browser. This information, usually in HTML/XHTML format, may enable navigation to another web pages, with hypertext links.Web pages can change your information frequently, as a dynamic web page, or stay all time, for all users, with the same contente, as a Static Web page. Varying filename extensions can be used, such as .htm, .html, or .php to name a few. Web pages often use graphic files to provide illustration. A web browser can have a Graphical User Interface, like Internet Explorer, Mozilla Firefox, or Opera, or can have a Command Line Interface, like Lynx.
Elements of a web page
A website can contain content which is able to be seen or heard by the end user. These elements include, but are not limited to:
• Text
• Graphics, typically GIF, JPEG or PNG formats
• Audio, typically MIDI or WAV formats
• Macromedia Flash
• Macromedia Shockwave
• Hyperlinks
A website can also contain content which is interpreted differently dependant upon the rendering browser and is typically not shown to the end user. These elements include, but are not limited to:
• Scripts, usually JavaScript
• Meta tags
• Cascading Style Sheets (CSS)
• Comments
Web pages will often require more screen space than is available for a particluar display resolution. Most modern browsers will place scrollbars in the window to allow the user to see all content. Scrolling horizontally is less previlant than vertical scrolling, not only because those pages do not print properly, but because it inconveniences the user moreso than vertical scrolling would. However, web pages may utilize page widening for various purposes.
A web page can either be a single HTML file, or made up of several HTML files represented using frames. Frames have been known to cause problems with navigation, printing, and search engine rankings[1], although these problems occur mostly in older-generation browsers. Their primary usage is to allow certain content which is usually meant to be static, such as page navigation or page headers, to remain in one place while the main content can be scrolled as necessary. Another merit of using a framed web page is that only the content in the "main" frame will be reloaded.[2] Frames are rendered very differently, depending on the host browser and for this reason, the usage of frames is typically frowned upon in professional web page development communities[3]. With design technologies such as CSS becoming more widespread in their usage, the effect frames provide can be made possible using a smaller amount of code and by using only one web page to display the same amount of content.
When web pages are stored in a common directory of a web server, they become a website. A website will typically contain a group of web pages that are linked together, or have some other coherant method of navigation. The most important web page to have on a website is the index page. Depending on the web server settings, this index page can have many different names, but the most common are index.htm and index.html. When a browser visits the home page for a website, or any URL pointing to a directory rather than a specific file, the web server will serve the index page to the requesting browser. If no index page is defined in the configuration, or no such file exists on the server, either an error or directory listing will be served to the browser.
When creating a web page, it is important to ensure it conforms to the World Wide Web Consortium (W3C) standards for HTML, CSS, XML and other standards. The W3C standards are in place to ensure all browsers which conform to their standards can display identical content without any special consideration for properitary rendering techniques. A properly coded web page is going to be accessible to many different browers old and new alike, display resolutions, as well as those users with audio or visual impairments.
Typically, web pages today are becoming more dynamic. A dynamic web page is one that is created server-side when it is requested, and then served to the end-user. These types of web pages typically do not have a permalink, or a static URL, associated with them. Today, this can be seen in many popular forums, online shopping, and even on Wikipedia. This practice is intended to reduce the amount of static pages in lieu of storing the relevant web page information in a database. Some search engines may have a hard time indexing a web page that is dynamic, so static web pages can be provided in those instances.
Viewing a web page
In order to view a web page, a web browser is needed. This is a type of software that can retrieve web pages from the internet. During the initial creation of a web page, before it is uploaded to the web server, any text editor can view it. Viewing a web page in a text editior will display the source code, not the final product.
Creating a web page
To create a web page, a text editor or a specialised HTML editor like Apple iWeb, Microsoft FrontPage, Macromedia Dreamweaver or Mozilla Composer is needed. These editors are also known as WYSIWYG editors. In order to upload a web page to a web server, an FTP client is needed. Tools supplied with the operating system can also perform thest tasks to a limited extent.
The design of a web page is highly personal. A design can be made according to ones own preference, or a pre-made web template can be used. Web Templates let web page designers edit the content of a web page without having to worry about the overall aesthetics.
Other ways of making a web page is to download specialized software, like a Wiki, CMS, or forum. These options allow for quick and easy creation of a web page which is typically dynamic. Wikipedia, WordPress, and Invision Power Board are examples of the above three web page options.
IP address
An IP address (Internet Protocol address) is a unique* number that devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP). Any participating network device — including routers, computers, time-servers, printers, internet fax machines, and some telephones — must have its own unique address.
An IP address can also be thought of as the equivalent of a street address or a phone number (compare: VOIP) for a computer or other network device on the internet. Just as each street address and phone number uniquely identifies a building or telephone, an IP address can uniquely identify a specific computer or other network device on a network.
An IP address can appear to be shared by multiple client devices either because they are part of a shared hosting web server environment or because a proxy server (e.g. an ISP or anonymizer service) acts as an intermediary agent on behalf of its customers, in which case the real originating IP addresses might be hidden from the server receiving a request. The analogy to telephone systems would be the use of predial numbers (proxy) and extensions (shared).
Domain names
A network lookup service, the Domain Name System (DNS), provides the ability to map domain names to a specific IP address. The purpose of domains is that humans are better at remembering names than arbitrary strings of numbers. It also allows an entity to change its IP addresses or reassign them without having to notify anyone except their DNS server.Another reason for DNS is to allow, for example, a web site to be hosted on multiple servers (each with its own IP address) which allows for rudimentary load balancing.
Dynamic and static IP addresses
IP addresses may either be assigned permanently (for example, to a server which is always found at the same address) or temporarily, from a pool of available addresses.
Dynamic IP addresses are issued to identify non-permanent devices such as personal computers or clients. Internet Service Providers (ISPs) use dynamic allocation to assign addresses from a small pool to a larger number of customers. This is used for dial-up access, WiFi and other temporary connections, allowing a portable computer user to automatically connect to a variety of services without needing to know the addressing details of each network.
Users with a dynamic IP may have trouble running their own email server as in recent years services such as mail-abuse.org [1] have collected lists of dynamic IP ranges and blocked them.
Dynamic IP address allocation requires a server to listen for requests and then assign an address. Addresses can be assigned at random or based on a predetermined policy. The most common protocol used to dynamically assign addresses is Dynamic Host Configuration Protocol (DHCP). DHCP includes a lease time which determines how long the requester can use an address before requesting its renewal, allowing addresses to be reclaimed if the requester goes offline.It is common to use dynamic allocation for private networks. Since private networks rarely have an address shortage, it is possible to assign the same address to the same computer on each request or to define an extended lease time. These two methods simulate static IP address assignment.
Static IP addresses are used to identify semi-permanent devices with constant IP addresses. Servers typically use static IP addresses. The static address can be configured directly on the device or as part of a central DHCP configuration which associates the device's MAC address with a static address.
IP versionsThe Internet Protocol has two primary versions in use. Each version has its own defintion of an IP address. Because of its prevalence, "IP address" typically refers to those defined by IPv4.

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