The links are underlined, as we have specified, but they are also blue, which we have not. When authors do not specify all possible styles, browsers use default styles to fill in the gaps. The interaction between author styles, browser default styles and user styles (the user’s own preferences) is another example of CSS’s conflict resolution rules.
Presenting a document to a user means converting it into a form usable by your audience. Browsers, like Firefox, Chrome, or Edge, are designed to present documents visually, for example, on a computer screen, projector, or printer. As we have mentioned before, CSS is a language for specifying how documents are presented to users — how they are styled, laid out, etc. Classes and IDs are case-sensitive, start with letters, and can include alphanumeric characters, hyphens, and underscores. A class may apply to any number of instances of any element. In addition to HTML, other markup languages support the use of CSS including XHTML, plain XML, SVG, and XUL.
Grouping selectors and rules
For another example of a browser default, in our web browser, the default font is “Times New Roman” displayed at size 16. Nearly none of the pages we visit the display in that font family and size, however. This is because the cascade defines that the second style sheets, which are set by the designers themselves, to redefine the font size and family, overriding our web browser’s defaults. Any style sheets you create for a web page will have more specificity than a browser’s default styles, so those defaults will only apply if your stylesheet does not override them. If you want links to be blue and underlined, you do not need to do anything since that is the default, but if your site’s CSS file says that links should be green, that color will override the default blue.
If you look at the way the style code cascades down, you can see which properties are being added and which ones are being changed along the way. With that code in place, the HTML page will render in the following format. After a CSS feature has been specified, then it is only useful for us in developing web pages if one or more browsers have implemented the feature.
Internal, External and Inline CSS Styles
Jennifer Kyrnin is a professional web developer who assists others in learning web design, HTML, CSS, and XML. Now that you have some understanding of what CSS is, let’s move on to Getting started with CSS, where you can start to write some CSS yourself. Another page also has some books,
mailing lists and similar fora, and
links to other directories. Cascading Style Sheets (CSS) is used to format the layout of a webpage. It can control the layout of multiple
web pages all at once. The aim here is to provide you with a toolkit for writing competent CSS and help you understand all the essential theory, before moving on to more specific disciplines like text styling and CSS layout.
So, for making HTML pages compatible with future browsers, it is good to start using CSS in HTML pages.
CSS Colors, Fonts and Sizes
For example, by default hyperlinks are styled in blue and they are underlined. Those styles come from a web browser’s default style sheet. If the web designer provides other instructions, however, the browser will need to know which instructions have precedence. All browsers have their own default styles, but many of those defaults (like the blue underlined text links) are shared across all or most major browsers and versions. We have known for years that designers want to develop their
own style sheets. However, we discovered that users, too, want the
option of influencing the presentation of their documents.
You can use CSS to apply multiple styles on a single HTML document. Those styles can affect the same element once, twice, or many more times over. As these style changes are written into the CSS file, they take a form of precedence from their location. In this short guide, you will learn what a cascading style sheet is, how to create one, and how to use it in your own HTML document.
Designer Style Sheets Override Browser Default Style Sheets
Chapter 16 will tell you how to point to
existing style sheets on the Web. Consider the styles applied on the CSS file to be a waterfall of sorts. The HTML document reads through the flow and applies whatever it finds along the way. The HTML page rendered the paragraph element with the value of red instead of sea green. This is because the next or most recent style applied to that element was the color red.
This saves time, shortens the code, and makes it not as prone to errors. You might have seen a website that fails to load completely and has a white background color with most of the text being blue and black. This means that the CSS part of the web page didn’t load correctly or it doesn’t exist altogether.
CSS
This means that the code has been written to turn the instruction in our CSS file into something that can be output to the screen. We’ll look at this process more in the lesson How CSS works. It is unusual for all browsers to implement a feature at the same time, and so there is usually a gap where you can use some part of CSS in some browsers and not in others. For this reason, being able to check implementation status is useful. A CSS stylesheet will contain many such rules, written one after the other.
- Any conflicts between the various style sheets are resolved by the
browser. - CSS lets you have multiple styles on one HTML page, therefore making the customization possibilities almost endless.
- Stylesheets can be added in the methods of inline, internal, and external.
- As CSS continues to evolve and new styles are introduced, web browsers have begun to implement modules that bring new CSS support into those browsers and give web designers powerful new styling tools to work with.
- To start using CSS, you don’t even have to
write style sheets.
Nearly all browsers nowadays
support CSS and many other
applications do, too. To write CSS, you don’t need more than a
text editor, but there are many tools available that make it even easier. Values may be keywords, such as “center” or “inherit”, or website development css cascading numerical values, such as 200px (200 pixels), 50vw (50 percent of the viewport width) or 80% (80 percent of the parent element’s width). CSS has a simple syntax and uses a number of English keywords to specify the names of various style properties.
CSS can also be used to define how web pages should look when viewed in other media than a web browser. For example, you can create a print style sheet that will define how the web page should print out. Because web page items like navigation buttons or web forms will have no purpose on the printed page, a Print Style Sheet can be used to “turn off” those areas when a page is printed. As there are so many things that you could style using CSS, the language is broken down into modules. Many of the documentation pages are organized around a particular module.
