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The Holy Grail refers to a web page layout which has multiple, equal height columns that are defined with style sheets. It is commonly desired and implemented, although the ways in which it can be implemented with current technologies all have drawbacks.〔(.appendTo: Solving the Holy Grail Layout )〕 Because of this, finding an optimal implementation has been likened to searching for the elusive Holy Grail. The limitations of CSS and HTML, the desirability of semantically meaningful pages that rank well in search engines, and the deficiencies of various browsers combine to create a situation in which there is no way to create this type of layout that would be considered totally correct. As the underlying technologies do not provide a proper solution, web designers have found various ways to work around the limitations. Common workarounds include changes in page structure, the addition of graphics, scripting, and the creative use of CSS. These methods are imperfect, inconvenient, and may even be considered abuse of the web standards and their intent. Upcoming web standards will deal with this and other layout issues in a much more elegant fashion. However, the problem will continue until these standards are finalized and widely implemented. == The problem == Many web pages require a layout with multiple (often three) columns, with the main page content in one column (often the center), and supplementary content such as menus and advertisements in the other columns (sidebars). These columns commonly require separate backgrounds, with borders between them, and should appear to be the same height no matter which column has the tallest content. Another common requirement is that, when a page does not contain enough content to fill the screen, the footer should drop to the bottom of the browser window instead of leaving blank space underneath. There are many obstacles to accomplishing this: * CSS, although quite useful for styling, currently has limited capabilities for page layout. * The height of block elements (such as div elements) is normally determined by their content. So two divisions, side by side, with different amounts of content, will have different heights unless their height is somehow set to an appropriate value. * HTML is meant to be used semantically; the purpose of HTML tags is to describe the type of content inside them. The appearance of a web page as rendered by a user agent should be determined independently by style rules. Many implementations misuse HTML by using tables for non-tabular data, or nesting multiple div tags without semantic purpose. Non-semantic use of HTML confuses users or user agents who are trying to discern the structure of the page content, and is an accessibility issue.〔(W3C: HTML5/Elements/Semantics )〕 * As search engines consider content in the beginning of a web page's source code to be more relevant, web designers desire the ability to place the content in the page source in an arbitrary order, without affecting the appearance of the page. * Because of incorrect rendering of content by different browsers, a method that works in a standards-compliant browser may not work in one that does not implement CSS correctly. 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「Holy Grail (web design)」の詳細全文を読む スポンサード リンク
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