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Tableless web design (or tableless web layout) is a web design philosophy eschewing the use of HTML tables for page layout control purposes.〔The term "tableless web design" refers to avoiding tables as a means of specifying general page or screen layout; they are a means for specifying and laying out tabular data 〕 Instead of HTML tables, style sheet languages such as Cascading Style Sheets (CSS) are used to arrange elements and text on a web page. The CSS1 specification was published in December 1996 by the W3C with the aim of improving web accessibility and emphasising the separation of presentational details in style sheets from semantic content in HTML documents. CSS2 in May 1998 (later revised in CSS 2.1 and CSS 2.2) extended CSS1 with facilities for positioning and table layout. Around the same time, in the late 1990s, as the dot-com boom led to a rapid growth in the "new media" of web page creation and design, there began a trend of using HTML tables, and their rows, columns and cells, to control the layout of whole web pages. This was due to several reasons: * the limitations at the time of CSS support in browsers; * the new web designers' lack of familiarity with the CSS standards; * the lack of knowledge of, or concern for the reasons (including HTML semantics and web accessibility) to use CSS instead of what was perceived as an easier way to quickly achieve the intended layouts, and * a new breed of WYSIWYG web design tools that encouraged this practice. The advantages of restricting the use of HTML tables to their intended and semantic purpose include improved accessibility of the information to a wider variety of users, using a wide variety of user agents. There are bandwidth savings as large numbers of semantically meaningless , and tags are removed from dozens of pages leaving fewer, but more meaningful headings, paragraphs and lists. Layout instructions are transferred into site-wide CSS stylesheets, which can be downloaded once and cached for reuse while each visitor navigates the site. Sites may become more maintainable as the whole site can be restyled or re-branded in a single pass merely by altering the mark-up of the specific CSS, affecting every page which relies on that stylesheet. New HTML content can be added in such a way that consistent layout rules are immediately applied to it by the existing CSS without any further effort. Some developers are now afraid to introduce a simple HTML table even where it makes good sense,〔 〕 some erring by the overuse of span and div elements, perhaps even with table-like rules applied to them using CSS.〔 〕 == Rationale == HTML was originally designed as a semantic markup language intended for sharing scientific documents and research papers online. Visual presentation was left up to the user. However, as the Internet expanded from the academic and research world into the mainstream in the mid-1990s, and became more media oriented, graphic designers sought ways to control the visual appearance of the Web pages presented to end users. To this end, tables and spacers (usually transparent single pixel .GIF images with explicitly specified width and height) have been used to create and maintain page layout. This causes a number of problems. Many web pages were designed with tables nested within tables, resulting in large HTML documents that use more bandwidth than documents with simpler formatting. Furthermore, when a table-based layout is linearized, for example when being parsed by a screen reader or a search engine, the resulting order of the content can be somewhat jumbled and confusing. In the late 1990s the first reasonably powerful WYSIWYG editors arrived on the market, which meant Web designers no longer needed a technical understanding of HTML to build web pages. Such editors indirectly encourage extensive use of nested tables to position design elements. As designers edit their documents in these editors, unnecessary code and empty elements can be added to the document. Furthermore, unskilled designers may use tables more than required when using a WYSIWYG editor. This practice can lead to many tables nested within tables as well as tables with unnecessary rows and columns. The use of graphic editors with slicing tools that output HTML and images directly also promote poor code with tables often having many rows of 1 pixel height or width. Sometimes many more lines of code are used to render content than the actual content itself. As the dotcom boom receded in 2001 and the web development industry shrank, coders with more industry experience were in higher demand. In a large number of cases UI development was carried out by coders with greater knowledge of good coding practice. It was around this time that many became critical of messy coding practices and the idea of tableless design began to grow. Cascading Style Sheets (CSS) were developed to improve the separation between design and content, and move back towards a semantic organization of content on the Web. The term "tableless design” implies the use of CSS rather than layout tables to position HTML elements on the page. HTML tables still have their legitimate place when presenting tabular information within web pages.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「tableless web design」の詳細全文を読む スポンサード リンク
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