The HTTP status code 503 is the most frequently seen server-side error code in the HTTP status code canon. 503 stands for “Service Unavailable” and is the code returned when a user requests a web page from a server that is overloaded or down for maintenance. When visiting a link from a popular and heavily trafficked link aggregation site like Reddit or Stumble Upon, it’s not uncommon to find that the deluge of traffic from the larger site had temporarily knocked the smaller web server offline.
The HTTP status code 404 is perhaps the best known of all HTTP error codes. The code indicates that your browser client successfully communicated with the server, but that the content you were looking for is not where the browser request indicated it should be (e.g. the article is actually at /pages/1.html/ and you requested it at /page/1.html instead).
HTTP status codes are a tool used by web servers to return information about the state of a server and/or the information it is serving up to the browser. The codes are divided into 5 general classes, each of which is signified by the first of the three digits. 1xx codes are informational and indicate a response from the server, 2xx codes indicate successful communication with the server, 3xx codes correspond to redirection requests, 4xx codes indicate a client error, and 5xx codes indicate a server error.
Link rot is a frustrating phenomenon on the world wide web wherein old or changed URLs no longer point to the resources they previously pointed to. For example, if a website used to have a directory structure for their articles like somehost.com/articles/001.html and they later switched to a new system like somehost.com/articles.php?001 all the old links would succumb to link rot and no longer direct to the correct resource (or, the site’s 404 page aside, to any resource at all).
The browser viewport is a technical term for the portion of the browser window which actually displays the content of the web site you are browsing. The viewport stands in direct contrast with the browser’s chrome (all the elements around the viewport such as the navigation buttons, address bar, status bar, and other GUI elements).
A status bar is a line of information, typically displayed at the bottom of a window in a graphical user interface. Although status bars have been around for decades, the most common place a typical computer user encounters a status bar is within a web browser. When hovering over a link, for example, such as this link to the front page of How-To Geek, most web browsers will display the actual address, http://www.howtogeek.com, in the status bar at the bottom of the window.
Web browsers have a web cache, a local temporary storage of downloaded web page elements (such as the page’s code and media components) intended to speed up your browsing experience. If you regularly visit a news web site, for example, elements like the site’s masthead and basic navigation icons can be pulled from the local cache instead of off the remote server.
Hyperlinks, typically referred to simply as links, are a core component of the web browsing experience. Hyperlinks take the form of text and images that, when activated by the user (or automatically by a script or web browser component), take the user to the document or file indicated by the link. Without the extensive use of hyperlinks, the smooth experience of jumping from one document to another on the web (such as jumping from the front page of How-To Geek to an article in the sidebar that interests you) would be greatly disrupted.
Private Browsing, also known as Private Windows and Incognito Mode, is a feature included in modern web browsers that allows you to browse the web in a special window wherein no data will be stored locally. There will be no links in the browser history, no cookie data, and no stored images or page content.
A browser history is the list of web sites you have visited using your web browser. Browsers typically allow you to view and delete the browser history, as well as set parameters such as how long of a browser history you wish to maintain (or if you want to maintain one at all).
In software engineering, extensibility is a system design principle focused on allowing an application to grow and provide additional features in the future. Web browsers are the most widespread example of system extensibility and even include bundles of additional features released as extensions, a direct nod to the design principle they are modeled after.
Forward compatibility, like backwards compatibility, is a compatibility concept used in system and product design. Unlike backwards compatibility, wherein a new system is designed to accept data from an old system (such as DVD players, invented long after the CD player, being designed to accept CDs), forwards compatibility is a design strategy wherein a product or system in the present is designed for maximum compatibility with future versions of itself.
In computing, backwards compatibility is the ability of a device to accept input from a previous generation of the product or technology. Backwards compatibility is very important to consumers in a variety of industries as it allows them to use previously purchased content with newer technology and products. For example, most Blu-ray players will also play DVDs and CDs even though it is not a requirement of the Blu-ray standard to be backwards compatible. Video game consoles are also frequently backwards compatible, as it encourages players to purchase the newest consoles if they know they can play previously purchased titles on them (the Nintendo WiiU, for example, can play all Wii games).
A daughterboard is any expansion board that is attached to the motherboard. This includes any expansion board like a networking interface card, a soundcard, a RAID controller, or other hardware expansion which is added to a computer via motherboard expansion slot. Daughterboards are typically only found on desktop and server machines, as mobile computers such as notebook computers and smartphones are either only expandable via USB or not at all.
A motherboard is the main printed circuit board (PCB) found in computers and other expandable electronic systems. The term motherboard specifically refers to printed boards with the potential for future expansion (as the motherboard serves as the “mother” which hosts and supports the expansion cards). While the term motherboard has been adopted to refer to just about any main board, for applications where there is no expansion (such as the main circuit board in a washing machine), it would be more accurate to refer to the board as the system board or mainboard.
Printed circuit boards (PCBs) are plastic boards that mechanically support and electrically connect the electronic components mounted on the board. The printed circuit board is the ubquitious but often unseen foundation of the entire modern electronics and computing revolution. From the guts of a tiny USB flash drive to the much larger motherboard inside your desktop computer, printed circuit boards are everywhere.
Introduced in 2003, ExpressCard is the successor of the widely adopted PC Card peripheral form factor and interface standard. Like the interface that preceded it, ExpressCard allows you to expand or upgrade notebook functionality by adding networking interface cards, sound cards, graphics cards, and other mobile upgrades.
PC Card is a form factor standard peripheral interface standard for notebook computers introduced in 1990. Originally intended to provide expanded storage space for mobile computers, the interface was quickly adapted for network cards and other upgrades. Although it underwent numerous revisions (designated by roman numerals I-III), it was eventually superseded by the Express Card standard in 2003. Several companies with high volume sales to government agencies and institutions still offer PC Card slots for backwards compatibility with older equipment.
The Personal Computer Memory Card International Association (PCMCIA) is an international standards body that defines, promotes, and oversees standards for notebook computer expansion devices such as models, external hard drives, and other peripherals. Over time the acronym PCMCIA has been applied not only to the organization itself but to the the form-factor of the physical PC cards used in notebook computers.
Commodity computing is a form of parallel computing. Unlike supercomputer setups that feature custom built hardware, commodity computing uses off-the-shelf hardware and computers to minimize costs. Companies use commodity computing because the cost of entry is low, parts are easy to replace, software and drivers are readily available, and the computers share a base architecture (such as Intel x86 or x64).
Parallel computing is a form of computation in which a large number of calculations are carried out simultaneously on hardware run in parallel. Parallel computation allows for some calculations and processes to be performed faster than serial computations (wherein each command must finish before the next is executed).
In modern email clients, both browser-based and stand-alone, you’ll find the digital answer to analog address books: contact lists. The most basic contact lists simply contain the name of the contact and their email address, but more robust contact lasts (such as those found in Outlook and Gmail) hold significantly more information like your contact’s physical mailing address, phone numbers, and other relevant information, including notes.
In computing, a black list is a list of items that a security algorithm or filter will always block. If you set up a filter in your email client to explicitly block the address of someone spamming you, for example, you’ve created a simple black list. Other black lists are automated, such as a black list that bans IP addresses at the server level after too many intrusion attempts are discovered from that IP address. Black lists are also used to filter content; when companies block entertainment or adult-content websites, they’re using a black list to restrict employee internet access.