Barrier-free Internet designates Internet offers, which can be used independently of all of their physical and/or technical possibilities without reservation. This closes both humans with and without handicaps, and users with technical (e.g. Textbrowser) or agecaused restrictions (e.g. Weak sights) as well as automatic search programs. Since this due to the innumerable yield, individually to be not completely reached one knows, speaks coined/shaped barriers also of barrier-poor or accessible. Technical term: Accessibility.

Statistically seen humans with handicaps are above average frequent in the Internet. It is little well-known that blind and sehbehinderte users web pages let themselves read out by software or be spent in Braille. Also or heavyhearing humans, whose first language is bearing language, need cut, special representational forms in the Internet on it. Therefore Internet offers must be created, which become fair their special needs.

Additionally to the consideration of the interests of handicapped ones it means "„barrier-free "“(contrary to "„obstruct-fairly "“) that completely generally nobody barriers into the way to be put to be supposed. Also the obligation is not to be imposed upon to non-disabled users to use with the call of Internet offers exactly the same hard and software configuration as the author of the offer. Apart from the accesibility it concerns thus with the topic Accessibility also platform independence - an Internet offer is to remain usable both with screen and with PDA, mobile phone, etc. It is to function independently of the used operating system and of the software (if this works RFC-conformal).

Internet techniques, which represent barriers

• Blind humans can read well structured text over a Braillezeile with appropriate software (screen reader). Pictures or text, which are contained in pictures, are inaccessible for blind ones and should be supplemented therefore with an alternative text. Frames are no obstacle, if they support the structure, for example navigation and contents separate.
• Sehschwache, in particular older humans, need scaling barness of the writing in the Browser, in order to be able to adapt character size to their visual efficiency.
• Persons with a color defective vision, e.g. a red/a green weak sight need strong contrasts and clear writings as well as control of the color of writing and background. Flashing one or animated texts represents a barrier.
• Sehbehinderte are disadvantaged with a navigation, which consists of pictures, Java applet or Flash objects.
• Persons with Spastiken or other motor disturbances, which cannot serve a mouse, must navigate with the keyboard. They move (usually with the tab key) by on the left of, form elements and other active objects on the side. So that a web page is well operated with the keyboard, it is important the fact that the elements in a meaningful order are headed for and that is at any time clearly recognizable, which has element the straight focus.
• humans often learned bearing language as the first language. For it the writing language a foreign language is usually with difficulty understandable and. Also acoustic contents cannot be taken up by humans. They should be replaced therefore by means of the visually perceptible contents or accompanied by them. Web pages for it, which are represented in bearing language, are barrier free.
• Humans with cognitive handicaps have usually problems to understand for a long time and pedantically formulated texts with difficult box sets and foreign words as well as complex Navigationen. Therefore it is meaningful to write web pages in so mentioned "„more easily language "“or to offer translations into "„easy language "“.
• Many of at present usual content management systems (CMS) produce sides, which are badly accessible for handicapped humans. Only very few systems or procedures support the authors with barrier-free input modes.
• The disregard of technical standards (e.g. correct coding of umlauts, valides HTML) produces web pages, only from certain Browsern (e.g. Internet Explorer) to be correctly represented.
• Navigation by active contents (e.g. Javascript, Flash) excludes users, who cannot to have installed and for different reasons no active contents implement let or be allowed to do the Plugins relevant for it.

Internet search machines indicate the WWW by automated programs, so-called Webcrawlern or also Robots. These programs notice a side similarly as sehbehinderte Surfer. They can evaluate usually only text. Pictures, animations and the like remain in most cases hidden for them. As rule of thumb is considered: Everything that prepares Sehbehinderten of problems, is also for Robots an obstacle.

A Verallgemeinerung of the rule of thumb is not possible however. Blind humans will receive possibly still another expenditure over an optional acoustic output. A Robot however, which cannot analyze tones, will be able to indicate then no information. Other around there are however nevertheless to analyze also examples, where human blind ones get no more information, Robots some more can (so for example structures or water-marks within pictures).

Fundamental techniques for barrier-free Internet

Basic condition for barrier-free Internet sides is the observance of Web standards (valides HTML/XHTML). One achieves the demanded strict separation from contents of (text, fig. etc.) and layout by the correct employment of Cascading Style Sheets (CSS). Compromises with the Design are not necessary. Some fundamental possibilities:

Positioning of elements

In order elements on a side to platzieren, can be used on the one hand table constructions, on the other hand can elements with Cascading Style Sheets by means of exact coordinates be platzieren. The source text is blown up by the use of tables unnecessarily, since also ranges must be defined, which are not used at all. With Cascading Style Sheets must be defined only elements, which are also needed. Also laps of individual elements (front and background elements in different Layern) are possible.

Particularly favourably is however above all the independence of the indicated position from in the source text. So the Head range of the visible CONTENTS can be defined only at the end in the HTML document. If this will provide e.g. with banners, which are disturbing for users with Handicap usually rather, then these are defined at the end of the source text. Thus users of screen readers must relevant contents not only uninteresting "„read "“, but can directly use.

Pictures for layout purposes

Often pictures are used only for layout purposes, not however for the information transfer. In order to keep the demanded standards to thus provide valides HTML one must provide pictures with an alternative text (old attribute). This can be disturbing e.g. for blind ones, why the value is left empty. The moreover one for the positioning of the pictures often complicated Tabellenkonstrukte is used. With the positioning of containers (DIVs) these can be dealt completely. If a picture only serves the layout/Design and transports no relevant information, then it should be defined as background picture in the Stylesheet (background image).

Interactive switching surfaces by CSS

Often Navigationen are programmed still by Javascript etc. This makes the source text unnecessarily extensive and locks users out, who deactivated Javascript support in their Browsern. With most switching surfaces in the Internet simply only background colour or - picture as well as text color and - decoration are exchanged. This is simpler by CSS around a multiple and the source text shrinks. This reduces naturally also the document size, whereby at the same time the transfer volume smaller will and the side is faster loaded.

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