In CSS, padding is a property that allows the author to specify how much space will be inserted between the element border and the element content. Negative values are not allowed.
Paper Prototype
A paper prototype is a paper sketch of an interface with just enough detail to make design decisions and usability evaluations relating to the function and flow of the interface, not the look.
PHP
PHP is an acronym for PHP hypertext Preprocessor. It is a server side scripting language for creating dynamic web pages. This means that it works within an HTML document to confer to it the capacity of generating content on demand. You can convert your site into a web application, not just a collection of static pages. If you've ever seen ASP, you'll be familiar with embedding code within an HTML page. Like ASP, PHP script is processed by the Web server. After the server plays with the PHP code, it returns plain old HTML back to the browser. This kind of interaction allows for some pretty complex operations
Pixel
The word "pixel" is derived from "picture element". In graphics, it refers to smallest resolvable rectangular area of an image. It is how how monitors divide the display screen into thousands or millions of individual dots. In CSS, a pixel is a relative unit of measure dependent on the viewing device. They are relative to monitor resolution in contrast to percent and em that are relative to a browser setting. Percent and em are considered best practice for accessibility.
Pixels Per Inch (PPI)
Pixels Per Inch (PPI) is the resolution of an image file. Web graphics and screenshots are made up of dots called pixels, and they usually contain 72 pixels per inch, though other resolutions are common. The horizontal and/or vertical density of an operating system's graphical display, from the point of view of the operating system (and in turn, of the applications and images running on it).
Plug-in
A module (either hardware or software) that adds a special feature to a larger system or program. For example, a program to allow a browser to play movies or to display Flash content. Plug-ins have accessibility issues.
Pluralistic Walkthrough
Pluralistic walkthroughs are when groups of users, developers, and usability experts walk through a task scenario. Group walkthroughs have the advantage of providing a diverse range of skills and perspectives to bear on usability problems. As with any inspection, the more people looking for problems, the higher the probability of finding problems. Also, the interaction between the team during the walkthrough helps to resolve usability issues faster.
Portable Document Format (PDF)
PDF is a proprietary file format developed by Adobe Systems Inc., as a way to publish documents electronically, with good formatting for printing, and document security (documents are generally read only). Originally it was in an image format. It was conceived as a way to make Adobe's Postscript printer language portable, and it mostly developed along the lines of press printing document production. Its prevalence can be attributed to the ease with which one can create PDF files. It is rare that one finds a PDF formatted for a computer screen. PDF has accessibility and usability issues. One of the main problems with PDF concerns accessibility issues associated with the document format, but this is only part of the problem. Even when users have the technology required to access information presented in this format, there can be content elements which have not received appropriate treatment to support accessibility (like using structural formatting for headings, etc. or text equivalents for images). Compared to HTML, PDF is slow and cumbersome. Many applications can save to formats other than their native file format, such as HTML, so this option when available is preferable to PDF, even when it needs to be cleaned up for the web.
Portable Network Graphics format (PNG)
PNG is an image format was developed as the successor to the GIF format. It has a more efficient compression algorithm than GIF.
Preferred Stylesheet
These style sheets are enabled by default (they are "on" when the page is loaded). They can then be disabled if the user selects an alternate style sheet. To make a style sheet preferred, the rel attribute is set to "stylesheet" and the style sheet is named with the title attribute.
Primary Navigation
Primary navigation is the general menu choices that are repeated on most (if not all) of the pages contained in the site. It is sometimes called the main menu. Primary navigation is sometimes referred to as global navigation or functional navigation. Primary navigation bars provide shortcuts to main sections on a website.
Property
In CSS, a property is named style attribute or parameter for a markup element specified in a stylesheet declaration, e.g. color, background, font-family, padding etc., that is assigned a certain value. Properties are always followed by a colon to separate them from their value pair. A declaration contains one or more properties the individual pieces of style to be applied to the selected element.
Prototype
A prototype is a partially completed mockup of your final website. Prototyping allows you to test certain parts of the final website, especially when it is incomplete. With many sites, this model can be as simple as paper-and-pencil drawings or as complex as actual working code.
