The IDL attribute is always going to use but might transform the underlying content attribute to return a value when you get it and is going to save something in the content attribute when you set it. In other words, the IDL attributes, in essence, reflect the content attributes. Most of the time, IDL attributes will return their values as they are really used. For example, the default type for element is used to create interactive controls for web-based forms in order to accept data from the user; a wide variety of types of input data and control widgets are available, depending on the device and user agent.
Unfortunately, there are no clear rules and the way IDL attributes behave in conjunction with their corresponding content attributes depends on the attribute. Most of the time, it will follow the rules laid out in the specification , but sometimes it doesn't. HTML specifications try to make this as developer-friendly as possible, but for various reasons mostly historical , some attributes behave oddly select. Some content attributes e.
The following examples are valid ways to mark up a boolean attribute:. To be clear, the values "true" and "false" are not allowed on boolean attributes. To represent a false value, the attribute has to be omitted altogether. Get the latest and greatest from MDN delivered straight to your inbox. Please check your inbox or your spam filter for an email from us. HTML attribute reference. Note: Although browsers and email clients may still support this attribute, it is obsolete.
Use CSS background-image instead. Contributors to this page: chrisdavidmills , Malvoz , mdnwebdocs-bot , JonathanPool , chharvey , mfuji09 , hrvoj3e , peterwilsoncc , sideshowbarker , ntutangyun , evilpie , Sheppy , fvsch , SphinxKnight , rudijuri , xgqfrms-GitHub , madmurphy , m59peacemaker , ChrisPermijo , mfluehr , shubhamg , diervo , Kinifwyne , piglovesyou , jswisher , leleofg , Tigt , myuller , rk17 , louuis , George , estelle , klez , kscarfone , Shokr , Techsin , haboqueferus , Srggamer , lmorchard , shirayuki , jonathan.
It participates in the table model.
The exact nature of this group is defined by the scope and headers attributes. Indicates whether controls in this form can by default have their values automatically completed by the browser. This mechanism is designed for use with Web-based certificate management systems. It can also be the destination for streamed media, using a MediaStream. Specifies the URL of an image file.
However, many older textbooks present them in Chapter 1. Hence, I shall list them here for completeness. BUT do not use these attributes. The foreground color of the texts is " blue ", on background color of " lightblue ". You can set different colors for the three types of links via attributes " link " for un-visited links , " vlink " for visited links , and " alink " for active link - the " alink " color shows up when you click on the link.
Comments are ignored by the browser. Comments are extremely important in programming to explain and document a section of programming codes and logic. HTML documents are textual and self-explanatory, comments are less important but still nice to have to describe the various part of the documents. Comments are also useful in temporarily disable a certain part of the HTML codes during development. In brief, a block element is always rectangular in shape, while an inline element spans a continuous run of characters. For example,. Note that the line breaks in the HTML codes are treated as white spaces and do not translate to new lines in the display.
Function: Establish six levels of document headings. Headings are usually displayed in bold, have extra white spaces above and below. Function: Draw a horizontal line or rule. The text is usually displayed in a fixed-width or monospace font. For example, my favorite Java's "Hello-world":. Function: Mark out a block of quote. Browsers typically indent the entire block to the right. They are simply markers and to be used together with CSS for applying custom formatting style. We shall describe them later in the CSS section. Nonetheless, it is important to note that NOT all browsers notably older IE versions support these new elements.
In a web page, figures are typically float alongside the text. However, IE 9 and IE 8 may have problems rendering these tags. Logical-style formatting tags specify the semantic meaning e. Logical styles should be used instead of physical styles. This is because physical styles deal with the appearance, which should be defined in style sheet, so as to separate the content and presentation.
Lorem curly quoted , consectetur adipisicing elit, sed do citation incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis sample exercitation ullamco laboris nisi ut code ex ea keyboard consequat. Duis aute irure dolor in reprehenderit in velit esse cillum dolore eu fugiat nulla pariatur. Excepteur insert occaecat delete non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. The contents are shown with a dotted underline.
Lorem abbr dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor HTML ut labore et dolore magna aliqua. I list them here for completeness, in case you need to read some old HTML codes. These elements are hardly used due to poor browser support, but presented here for completeness.
Highlighting certain texts, such as keywords. By default, it is shown with bright yellow background, similar to highlighter's marking. Hence, these characters are reversed and cannot be used in the text directly. The commonly used entity references are as follows there are many many more, refer to the HTML reference - I like the arrows, Greek symbols, and the mathematical notations. Entity reference is case sensitive. As mentioned earlier, browsers ignore extra whitespaces blanks, tabs, newlines.
That is, multiple whitespaces are treated as one single whitespace. List-related tags are meant for marking up a list of items. HTML supports three types of lists: ordered list , unordered list and definition list. Function: An unordered list is shown with a bullet in front of each item. Items in an ordered list are numbered automatically by the browser. The syntax is similar to the unordered list. The "unordered list" and "ordered list" are used in most of the HTML documents. But I don't find many web pages using the "definition list". You can nest any types of lists ordered list, unordered list.
Table-related tags are meant for tabulating data. Use style sheet for formatting instead. The basic unit of a table is a cell. Cells are grouped into row. Rows are grouped to form the table. This corresponds well to the "row-centric" approach in the display. The now-preferred approach is to use CSS again! Function: Set up each individual cell of a row of a table. Function: Used to define a header, body and footer sections for a table. Browser may duplicate the header or footer when breaking the table across multiple pages in print-out.
They can also be used to apply styles to each of the sections. An HTML table is row-centric. It consists of rows of cells. But the features are really limited.
Only a few properties could be applied on columns: border , background , width and visibility. Function: to set up a hyperlink pointing to the url in " href " hypertext reference attribute. Instead of displaying the targeted page pointed to by href in the current browser's window.
But it seems to be back in HTML5. A URL uniquely identifies a piece of resource over the Internet.
Comprehensive CSS3 Command List, With Descriptions And Typical Mark Up
A URL is made up of 4 parts as follows:. An absolute URL is fully qualified , e. Rule of Thumb: Always use relative URLs for referencing documents in the same server for portability i. Use absolute URLs only for referencing resources from a different server. Internal links points to resources in the same website including anchor point in the current page. External links point to another website.
reStructuredText Markup Specification
In HTML 4. This is similar to the implicit anchor name setup via the id attribute described earlier. For example:. Image used as hyperlink anchor automatically gets a border. The original aim of HTML is to let the content providers concentrate on the contents of the document and leave the appearance to be handled by the browsers. The browsers then decide on how to display or present the contents in the browser's window for the web surfers.
However, HTML has gone out-of-control in the early years. Many markup tags and attributes were created for marking the appearance and the display styles e. These tags flood the document and make creation and maintenance of the contents extremely difficult. Furthermore, over the years, we have engaged graphic designers to work on the appearance and leave the content providers to focus on the contents.
Hence, there is a need to separate the contents and presentation of the HTML document. It allows web graphic designers to spice up the web pages, so that the content providers can focus on the document contents with HTML. A style rule is used to control the appearance of HTML elements such as their font properties e. This is the same as the styles in any publishing software like WinWord or LaTex.
The word cascading means that multiple style rules can be applied to the same HTML element. The browser follows a certain cascading order in finalizing a style to format the HTML element in a predictable fashion. Take note that CSS is a language with its own syntaxes. On CSS, you could select inspect an HTML element, and it will show you all the cascading style rules that are applied to that elements from all the sources inline, embedded, external , and how the rules were merged and conflicts were resolved.
You can temporarily disable a rule, and edit a rule to check the effect instantly. Get it and start to inspect the web pages of your favorite site. CSS is a language by itself. How many syntaxes you have to know to program the web?! To apply inline style to an HTML element, include the list of style properties in the style attribute of the opening tag. This paragraph uses 20px inside this span but default font size here. Take note that the name and value are separated by colon ':' , and the name:value pair are separated by semicolon ';' , as specified in the CSS syntax. The scope of an inline style is limited to that particular element.
Hence, inline style should be avoided and only be used sparsely for touching up a document , e. For example, we define these style rules in a file called " TestExternal. The main advantage of external style sheets is that the same set of styles can be applied to all HTML pages in your website to ensure uniformity in presentation. External style sheet is the now-preferred approach. Inline styles have the highest priority, followed by internal styles, and followed by external styles. Many but not all CSS properties, such as color and font-family , affect not only the elements selected by the selector, but also inherited by their descendants.
Inheritance is a big time-saver for designing styles.
You then override the default properties for specific elements, if needed. Some properties such as border , margin , padding , width , height , background-color are not inherited. This is for good reason. You can use a special property-value called " inherit " to inherit the property from its ancestor. We can force the inheritance by assigning a special value " inherit " as shown in the Class Selector.
If a property is not defined for an element and is inheritable, it will be inherited from the nearest ancestor. Specificity means that "the more specific the selector, the stronger the rule". The ID-selector is the most specific and takes precedence ; followed by Class-selector; and followed by the general Tag-selector. If the "Law of Specificity" cannot resolve the conflict, apply the "Law of Locality".
The style-rule that read in last by the browser takes effect. In the above example, there are two ID-selector for id1 , the latter takes effect. You can override all the cascading rules by appending a special property-value! To use CSS to style your website for good and consistent look and feel, you need to properly structure and partition your web pages.
They can be used to create partitions in an HTML document to represent logical sections such as header, content, footer, highlight text, and so on. They shall be further qualified with id or class attribute, and attached with CSS styles selected via the ID-selector or Class-selector. Old HTML pages uses tables and frames, which should be avoided.
A CSS ID-selector , which begins with a ' ' followed by an id value, selects a unique element because id value is supposed to be unique in the document. A CSS Class-selector , which begins with a '. As illustrated in the previous example, a CSS selector can select a set of HTML elements based on a tag name, b id attribute, c class attribute. In addition, you can write a CSS selector to select elements based on combination of tag, id and class, and much more.
CSS is humongous! I shall list the frequently-used types of CSS selectors here. You can apply the same style definitions to multiple selectors, by separating the selectors with a commas ' ,'. The syntax is,. The selector-x could be any kind of selectors, such as Tag-selector, Class-selector, or ID-selector. You can define a style rule that takes effect only when a tag occurs within a certain contextual structure, e. To create a descendant selector , list the tags in their hierarchical order, with no commas separating them commas are meant for grouping selectors.
The style is applied to tag T2 , only if it follows immediately after T1. T1 and T2 are siblings in the same hierarchical level. The Generic-Class Selector , which begins with a dot '. Take note that the class attribute may contain multiple values. This means that you can apply multiple class style rules to an HTML element.
The selector T. C selects all tag-name T with classname of C. This is a restricted form of the Generic-Class selector, which applies to the specific tag-name only. This subclass mechanism allows us to apply different styles to different subclass of a particular element. Note: Do NOT start a class-name with a number! This is the same restriction for identifiers in most of the programming languages. The ID-selector, begins with a ' ' followed by the id value, selects a specific element with the given unique id value. Recall that the id value must be unique in an HTML document.
Same as above but only if the id is defined under the tag. Since id value is supposed to be unique, this serves more as proper documentation.
- Publisher Description;
- What is Kobo Super Points?.
- Join Kobo & start eReading today!
- Cascading Style Sheets - Wikipedia;
- Content versus IDL attributes!
Take note that colon " : " is used to identify pseudo classes instead of ". The anchor pseudo-classes can be combined with ID-selectors as a Descendant-selector, so that the appearance of the links is different for the different divisions of the document, e. They are called pseudo-elements because they select a portion of an element that is hard to be marked out e.
You can restrict the selection by applying id or class. For example, p. In CSS3, pseudo-elements are prefixed with 2 colons to differentiate with the pseudo-class, i. The :before and :after pseudo-elements lets you select elements and add content before or after the elements. Select the user-selected-text on the screen. You are only allow to set the color and background-color properties. The :not S selector lets you select elements not meeting the criterion in selector S. For example, :not. I shall present the commonly-used properties such as color, font, text, margin, border, padding.
Many CSS properties, such as width , height , margin , border , padding , font-size and line-height , require a length measurement. There are two types of length measurements: relative to another length property and absolute e. There shall be no space between the number and the unit, as space is used to separate multiple values. To add to the confusion, some properties, such as line-height , can also accept a bare number, without a unit.