9. duben Cascading Style Sheets Kolekce metod pro grafickou úpravu webových stránek. Co to je? Kaskádové styly = CSS – první návrh normy. Download Citation on ResearchGate | Eric Meyer o CSS – ovládněte kaskádové styly! / | Vyd. 1. Překlad z angličtiny }. Smart catalogue of educational materials focused on a relation of geoinformation technologies and environment. The application has been developed as a part.
|Genre:||Health and Food|
|Published (Last):||22 March 2013|
|PDF File Size:||12.61 Mb|
|ePub File Size:||13.91 Mb|
|Price:||Free* [*Free Regsitration Required]|
Cascading Style Sheets CSS is a style sheet language used to describe the presentation semantics the look and formatting of a document written in a markup language.
CSS is designed primarily to enable the separation of document content written in HTML or a similar markup language from document presentation, including elements such as the layoutcolorsand fonts. CSS can also allow the same markup page to be presented in different styles for different rendering methods, such as on-screen, in print, by voice when read out by a speech-based browser or screen reader and on Braille -based, tactile devices. While the author of a document typically links that document to a CSS style sheet, readers can use a different style sheet, perhaps one on their own computer, to override the one the author has specified.
CSS specifies a priority scheme to determine which style rules apply if more than one rule matches against a particular element. In this so-called cascadepriorities or weights are calculated and assigned to rules, so that the results are predictable. CSS has a simple syntax and uses a number of English keywords to specify the names of various style properties. A style sheet consists of a list of rules. Each rule or rule-set consists of one or more selectors and a declaration block.
A declaration-block consists of a list of declarations in braces. Each declaration itself consists of a propertya colon: If there are multiple declarations in a block, a semi-colon ; must be inserted to separate each declaration. In CSS, selectors are used to declare which of the markup elements a style applies to, a kind of match expression. Selectors may apply to all elements of a specific type, or only those elements that match a certain attribute; elements may be matched depending on how they are placed relative to each other in the markup code, or on how they are nested within the Document Object Model.
Pseudo-classes are another form of specification used in CSS to identify markup elements, and in some cases, specific user actions to which a particular declaration block applies.
An often-used example is the: It is appended to a selector as in a: Other pseudo-classes and pseudo-elements are, for example,: A special pseudo-class is: A pseudo-class selects entire elements, such as: Selectors may be combined in other ways too, especially in CSS 2. CSS allows authors to move much of that information to kzskadove separate style sheet resulting in considerably simpler HTML markup. Headings h1 elementssub-headings h2sub-sub-headings h3etc. In print and on kaskadovf screen, choice of fontsizecolor and emphasis for these elements is presentational.
Prior to CSS, document authors who wanted to assign such typographic characteristics to, say, all h2 headings stylh to use the HTML font and other presentational elements for each occurrence of that heading type. The additional presentational markup in the HTML made documents more complex, and generally more difficult to maintain. In CSS, presentation is separated from structure.
In print, CSS can define color, font, text alignment, size, borders, spacing, layout and many other typographic characteristics. It can do so independently for on-screen and printed views. CSS also defines non-visual styles such as the speed and emphasis with which text is read out by aural text readers.
It has therefore deprecated the use of all the original presentational HTML markup. CSS information can be provided by various sources. Multiple style sheets can be imported. Different styles can be applied depending on the output device being used; for example, the screen version can be quite different from the printed version, so that authors can tailor the presentation appropriately for each medium.
The style sheet with the highest priority controls the content display. Declarations not set in the highest priority source are passed on by a source of lower priority such as the user agent style.
This process is called cascading. One of the goals of CSS is also to allow users greater control over presentation. Someone who finds red italic headings difficult to read may apply a different style sheet. Depending on their browser and the web site, a user may choose from various style sheets provided by the designers, may remove all added style and view the site using the browser’s default styling, or may override just the red italic heading style without altering other attributes.
Such a file is stored locally and is applicable if that has been specified in the browser options. Style sheets have existed in one form or another since the beginnings of SGML in the s.
Cascading Style Sheets were developed as a means for creating a consistent approach to providing style information for web documents.
As HTML grew, it came to encompass a wider variety of stylistic capabilities to meet the demands of web developers. This evolution gave ksakadove designer more control over site appearance but at the cost of HTML becoming more complex to write and maintain. Variations in web browser implementations i. ViolaWWW and WorldWideWeb  made consistent site appearance difficult, and users had less control over how web content was displayed.
Robert Cailliau wanted to separate the structure from the presentation. To improve web presentation capabilities, nine different kaskadpve sheet languages were proposed to the World Wide Web Consortium ‘s W3C www-style mailing list. Of the nine proposals, two were chosen as the foundation for what became CSS: One style sheet could inherit or “cascade” from another, permitting a mixture of stylistic preferences controlled equally by the site designer and user.
It organized a workshop toward that end chaired by Steven Pemberton. Lie and Bos were the primary technical staff on this aspect of the project, with additional members, including Thomas Reardon of Microsoftparticipating as well. Early inthe ERB was split into three working groups: It was published as a W3C Recommendation on May 12, CSS level 3, which was started inis still under development as of This meant that already published standards like CSS 2.
Although the CSS1 kaskadovr was completed in and Microsoft’s Internet Explorer 3  was released in that year featuring some limited support for CSS, it was more than three years before any web browser achieved near-full implementation of the specification. Other browsers followed soon afterwards, and many of them additionally implemented parts of CSS2. Even though early browsers such as Internet Explorer 3  and 4and Netscape 4. This was a serious obstacle for the adoption of CSS.
When later ‘version 5’ browsers began to offer a kwskadove full implementation of CSS, they were still incorrect in certain areas and were fraught with inconsistencies, bugs and other quirks. The proliferation of such CSS-related inconsistencies and even the variation in feature support has made it difficult for designers to achieve a consistent appearance across platforms.
Some authors resorted to workarounds such as CSS hacks and CSS filters to obtain consistent results across web browsers and platforms.
Category:Cascading Style Sheets
Some CSS2 properties that no browser successfully implemented were dropped, and in a few cases, defined behaviors were changed to bring the standard into line with the predominant existing implementations. In the past, some web servers were sgyly to serve all documents with the filename extension. CSS has various levels and profiles.
Profiles are typically a subset of one or more levels of CSS built for a particular device or user stjly. Currently there are profiles for mobile devices, printers, and television sets. Profiles should not be confused with media types, which were added in CSS2. A superset of CSS1, CSS2 includes a number of new capabilities like absolute, relative, and fixed positioning of elements and z-indexthe concept of media types, support for aural style sheets and bidirectional text, and new font xtyly such as shadows.
It was returned to Candidate Recommendation status on 19 July and was updated twice in However, since changes and clarifications were made to the prose it went back to Last Call Working Draft on 7 December Later it went into Proposed Recommendation on 12 April Instead of defining all features in a single, large specification like CSS2, CSS3 is divided into several separate documents called “modules”.
Learn css in Y Minutes
Each module adds new capability or extends features defined in CSS2, over preserving backward compatibility. The earliest CSS3 drafts were published in June Due to the modularization, different modules have different stability and are in different status.
Because not all browsers correctly parse CSS code, developed coding techniques known as CSS hacks can either filter specific browsers or target specific browsers generally both are known as CSS filters. The former can be defined as CSS filtering hacks and the latter can be defined as CSS targeting hacks and both of which can be used to hide or show parts of the CSS to different browsers.
This is achieved either by exploiting CSS- handling quirks or bugs in the browser, or by taking advantage of lack of support for parts of the CSS specifications.
Because very early web browsers were either completely incapable of handling CSS, or render CSS very poorly, designers today often routinely use CSS filters that completely prevent these browsers from accessing any of the CSS. An example of a well-known CSS browser bug is the Internet Explorer box kaskadovf bugwhere box widths are interpreted incorrectly in several versions of the browser, resulting in blocks that are too narrow when viewed in Internet Explorer, but syly in standards-compliant browsers.
Even today, these problems continue to make the business of CSS design more complex and costly than it was intended to be, and cross-browser testing remains a necessity.
Other reasons for continuing non-adoption of CSS are: CSS frameworks are pre-prepared libraries that are meant to allow for easier, more standards-compliant styling of web pages using the Cascading Style Sheets language. Like programming and scripting language libraries, CSS frameworks are usually incorporated as external.
They provide a number of ready-made options for designing and laying out the web page. While many of these frameworks have been published, some authors use them mostly for rapid prototyping, or for learning from, and prefer to ‘handcraft’ CSS that is appropriate to each published site without the design, maintenance and download overhead of having many unused features in the site’s styling.
There are four possible values of the position property.
If an item is positioned in any way other than staticthen the further properties topbottomleftand right are used to specify offsets and positions. The float property may have one of three values. Absolutely positioned or fixed items cannot be floated.
Other elements normally flow around floated items, unless they are prevented from doing so by their clear property. Cascading Style Sheets cs: Cascading Style Sheets da: Cascading Style Sheets et: Hojas de estilo en cascada eo: Feuilles de style en cascade ga: