Liquid versus fixed layouts
On the web the designer has no control over several factors, including the size of the browser window, the web browser used, the input devices used (mouse, touch screen, voice command, text, cell phone number pad, etc.) and the size and characteristics of available fonts.
Some designers choose to control the appearance of the elements on the screen by using specific width designations. This control may be achieved through the use of a HTML table-based design, and/or through the use of CSS. Whenever the text, images, and layout of a design do not change as the browser changes, this is referred to as a fixed width design. Proponents of fixed width design prefer the control over the look and feel of the site and the precision placement of objects on the page. Other designers choose a liquid design. A liquid design enables the design moves to flow content into the whole screen, or a portion of the screen, no matter what the size of the browser window. Proponents of liquid design prefer to use all the screen space available. Liquid design can be achieved through the use of CSS, by avoiding styling the page altogether, or by using HTML tables set to a percentage of the page. Both liquid and fixed design developers must make decisions about how the design should degrade on higher and lower screen resolutions. Sometimes the pragmatic choice is made to flow the design between a minimum and a maximum width. This allows the designer to avoid coding for the browser choices making up the long tail, while still using all available screen space. Depending on the purpose of the content, a web designer may decide to use either fixed or liquid layouts on a case-by-case basis.
Similar to liquid layout is the optional fit to window feature with Adobe Flash content. This is a fixed layout that optimally scales the content of the page without changing the arrangement or text wrapping when the browser is resized.
Flash
Adobe Flash (formerly Macromedia Flash) is a proprietary, robust graphics animation/application development program used to create and deliver dynamic content, media (such as sound and video), and interactive applications over the web via the browser.
Flash is not a standard produced by a vendor-neutral standards organization like most of the core protocols and formats on the Internet. Flash is much more restrictive than the open HTML format, though, requiring a proprietary plugin to be seen, and it does not integrate with most web browser UI features like the "Back" button unless a hyperlink is programmed to link a new html page from the Flash file, in which case the animation of the previous page would reset. However, those restrictions may be irrelevant depending on the goals of the web site design.
Many graphic artists use Flash because it gives them exact control over every part of the design, and anything can be animated and generally "jazzed up". Some application designers enjoy Flash because it lets them create applications that do not have to be refreshed or go to a new web page every time an action occurs. Flash can use embedded fonts instead of the standard fonts installed on most computers. There are many sites which forgo HTML entirely for Flash. Other sites may use Flash content combined with HTML as conservatively as gifs or jpegs would be used, but with smaller vector file sizes and the option of faster loading animations. Flash may also be used to protect content from unauthorized duplication or searching. Alternatively, small, dynamic Flash objects may be used to replace standard HTML elements (such as headers or menu links) with advanced typography not possible via regular HTML/CSS (see Scalable Inman Flash Replacement).
Flash detractors claim that Flash websites tend to be poorly designed, and often use confusing and non-standard user-interfaces. Up until recently, search engines have been unable to index Flash objects, which has prevented sites from having their contents easily found. This is because many search engine crawlers rely on text to index websites. It is possible to specify alternate content to be displayed for browsers that do not support Flash. Using alternate content also helps search engines to understand the page, and can result in much better visibility for the page. However, the vast majority of Flash websites are not disability accessible (for screen readers, for example) or Section 508 compliant. An additional issue is that sites which commonly use alternate content for search engines to their human visitors are usually judged to be spamming search engines and are automatically banned.
The most recent incarnation of Flash's scripting language (called "ActionScript", which is an ECMA language similar to JavaScript) incorporates long-awaited usability features, such as respecting the browser's font size and allowing blind users to use screen readers. Actionscript 2.0 is an Object-Oriented language, allowing the use of CSS, XML, and the design of class-based web applications.
CSS versus tables
Back when Netscape Navigator 4 dominated the browser market, the popular solution available for designers to lay out a Web page was by using tables. Often even simple designs for a page would require dozens of tables nested in each other. Many web templates in Dreamweaver and other WYSIWYG editors still use this technique today. Navigator 4 didn't support CSS to a useful degree, so it simply wasn't used.
After the browser wars subsided, and the dominant browsers such as Internet Explorer became more W3C compliant, designers started turning toward CSS as an alternate means of laying out their pages. CSS proponents say that tables should be used only for tabular data, not for layout. Using CSS instead of tables also returns HTML to a semantic markup, which helps bots and search engines understand what's going on in a web page. All modern Web browsers support CSS with different degrees of limitations.
However, one of the main points against CSS is that by relying on it exclusively, control is essentially relinquished as each browser has its own quirks which result in a slightly different page display. This is especially a problem as not every browser supports the same subset of CSS rules. For designers who are used to table-based layouts, developing Web sites in CSS often becomes a matter of trying to replicate what can be done with tables, leading some to find CSS design rather cumbersome due to lack of familiarity. For example, at one time it was rather difficult to produce certain design elements, such as vertical positioning, and full-length footers in a design using absolute positions. With the abundance of CSS resources available online today, though, designing with reasonable adherence to standards involves little more than applying CSS 2.1 or CSS 3 to properly structured markup.
These days most modern browsers have solved most of these quirks in CSS rendering and this has made many different CSS layouts possible. However, some people continue to use old browsers, and designers need to keep this in mind, and allow for graceful degrading of pages in older browsers. Most notable among these old browsers are Internet Explorer 5 and 5.5, which, according to some web designers, are becoming the new Netscape Navigator 4 — a block that holds the World Wide Web back from converting to CSS design. However, the W3 Consortium has made CSS in combination with XHTML the standard for web design.