Css2 Design and Development Guide

CSS2 is a powerful styling language that has been a cornerstone of web development for decades. It's used to add visual effects and layout controls to web pages.

One of the key features of CSS2 is its ability to use relative units, such as percentages and ems, to define font sizes and widths. This allows for more flexible and responsive designs.

CSS2 also introduced the concept of pseudo-classes, which enable developers to apply styles based on user interactions, such as hover and active states. This adds a whole new level of interactivity to web pages.

With CSS2, developers can also use the box model to control the layout of elements, including padding and borders. This makes it easier to create complex layouts and designs.

CSS Basics are the foundation of styling web pages. They provide the building blocks for creating visually appealing and user-friendly websites.

CSS stands for Cascading Style Sheets, which is a styling language used to control the layout and appearance of web pages. It was first introduced in 1996 as CSS1, and since then, it has evolved to become a crucial part of web development.

To write CSS, you need to know the basics of HTML, the language used to create web pages. CSS styles are applied to HTML elements to change their appearance. For example, you can use CSS to change the color, font, and size of text on a web page.

CSS selectors are used to target specific HTML elements and apply styles to them. There are different types of selectors, including element selectors, class selectors, and ID selectors.

CSS can be used with any structured document format, such as XML. XML depends more on style sheets than HTML because authors can make up their own elements that user agents don't know how to display.

To display an XML document in a document-like fashion, you must declare which elements are inline-level and which are block-level. The first rule declares INSTRUMENT to be inline.

A visual user agent could format an XML document as: Still, the text isn't formatted the way you would expect. For example, the headline font size should be larger than the rest of the text.

To improve the presentation of an XML document, you can add more rules to the style sheet. This will allow you to further improve the presentation of the document.

As we've learned in our CSS basics article, CSS1 introduced several important features that are still used today.

The CSS1 specification defined a new way of styling HTML documents, making it easier to separate presentation from structure.

One of the key additions to CSS1 was the ability to specify font styles, including font family, size, and color.

CSS1 also introduced the concept of IDs and classes, which are still used to target specific elements in a document.

IDs are used to identify a single element, while classes can be used to target multiple elements.

The CSS1 specification also defined the box model, which includes the content area, padding, and border.

Understanding the box model is crucial for creating responsive and visually appealing designs.

CSS1 also introduced the concept of inheritance, which allows styles to be passed down from parent elements to child elements.

Inheritance is a powerful feature that can simplify your CSS code and make it more maintainable.

CSS Structure is built on a set of design principles that ensure flexibility and maintainability. One of these principles is forward and backward compatibility, which means that CSS2 user agents can understand CSS1 style sheets, and vice versa.

This allows webmasters to easily update their sites without worrying about breaking existing styles. For example, if an organization changes its background color, only one file needs to be changed.

CSS2 also emphasizes vendor, platform, and device independence, enabling documents to remain consistent across different browsers and devices. This is achieved through the use of style sheets that are vendor and platform independent.

Here are the key design principles of CSS2:

The Processing Model is a crucial part of how user agents work with CSS. It's a conceptual model that outlines the steps a user agent takes to process a source document.

In this model, a user agent first parses the source document and creates a document tree. This is the foundation of the processing model, and it's essential for applying styles to the document.

The user agent then identifies the target media type, which determines the formatting algorithm to use. For example, if the target medium is the screen, the user agent applies the visual formatting model.

The user agent retrieves all style sheets associated with the document that are specified for the target media type. These style sheets are then used to annotate every element of the document tree.

The annotated document tree is then used to generate a formatting structure. This structure closely resembles the document tree but may also differ significantly, especially when authors use pseudo-elements and generated content.

The formatting structure is then transferred to the target medium, such as being printed, displayed on the screen, or rendered as speech.

Here are the steps of the processing model outlined:

An external style sheet is a great way to keep your CSS organized and efficient. You create a .css file and then link it to your HTML page, making it easy to use the same styles throughout your site without having to write them out again and again.

One of the main benefits of using an external style sheet is that it saves a lot of your page's loading time. This is because you're not repeating the same CSS styles in every HTML file, which can make your pages load faster.

Having all your styles in one place makes it much more convenient to manage your site's design. You can make changes to the style sheet and they'll be reflected across your entire site.

External style sheets are especially useful when you have many HTML attributes that you want to use consistently. By linking to a single style sheet, you can apply those styles to every page on your site with ease.

Here are some benefits of using an external style sheet at a glance:

By using an external style sheet, you can simplify site maintenance and retain a consistent look and feel throughout your site. This is one of the key principles of CSS design, which aims to make it easy to change the style sheet without impacting the underlying markup.

CSS2 has improved table handling, introducing properties like display, which has ten values including table, inline-table, and table-cell.

These properties can be applied to a cell, a column, or a column-group, just like the HTML attributes for table cells.

The new properties cell-spacing and border-collapse influence how cell borders interact, while table-layout determines whether the browser can resize the table.

The caption-side property functions like the ALIGN attribute on the CAPTION tag, controlling where the caption is displayed.

There's also a speak-header-cell property that controls how header cells are handled by speech-generating browsers.

The section on tables is still evolving, with a third of the chapter marked "UNDER CONSTRUCTION" and likely to change before the specification is finalized.