Cascading Style Sheets

Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language. Although most often used to set the visual style of web pages and user interfaces written in HTML and XHTML, the language can be applied to any XML document, including plain XML, SVG and XUL, and is applicable to rendering in speech, or on other media. Along with HTML and JavaScript, CSS is a cornerstone technology used by most websites to create visually engaging webpages, user interfaces for web applications, and user interfaces for many mobile applications.

CSS is designed primarily to enable the separation of document content from document presentation, including aspects such as the layout, colors, and fonts. This separation can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, enable multiple HTML pages to share formatting by specifying the relevant CSS in a separate .css file, and reduce complexity and repetition in the structural content, such as semantically insignificant tables that were widely used to format pages before consistent CSS rendering was available in all major browsers. CSS makes it possible to separate presentation instructions from the HTML content in a separate file or style section of the HTML file. For each matching HTML element, it provides a list of formatting instructions. For example, a CSS rule might specify that "all heading 1 elements should be bold", leaving pure semantic HTML markup that asserts "this text is a level 1 heading" without formatting code such as a <bold> tag indicating how such text should be displayed.

DF-4

The Dong Feng 4 (Chinese: 东风4, meaning "East Wind") or DF-4 (also known as the CSS-3) is a two-stage Chinese Intercontinental ballistic missile with liquid fuel (Nitric acid/Unsymmetrical dimethylhydrazine). It was thought to be deployed in limited numbers in underground silos beginning in the 1970s and early 1980s. The Dong Feng 4 has a takeoff thrust of 1,224.00 kN, a takeoff weight of 82000 kg, a diameter of 2.25 m, a length of 28.05 m and a fin span of 2.74 m. The range of the Dong Feng 4, which is equipped with a 2,190 kg nuclear warhead with 3.3 Mt yield, with a nominal range of 5,500 km. This gives it sufficient range to strike targets as far away as Russia, India, and American bases in the Pacific. The missile uses an inertial guidance system, resulting in a large CEP of 1,500 meters.

History

The decision to develop the DF-4 was made in 1965 in response to the U.S. ballistic missile submarine patrols that began operating out of Guam. The missile's designer has been variously identified as Ren Xinmin or Tu Shou'e [屠守锷], and it was produced at Factory 211 (Capital Astronautics Co. [首都航天机械公司], also known as Capital Machine Shop [首都机械厂]).