The Webmaster's Lexicon: C

Cascading Style Sheets	CSS A mechanism that allows authors and readers to attach the same style (e.g. fonts, colors and spacing) to multiple HTML documents. The CSS language is human readable and writable, and expresses style in common desktop publishing terminology. One of the fundamental features of CSS is that style sheets cascade; authors can attach a preferred style sheet, while the reader may have a personal style sheet to adjust for human or technological handicaps.
CDF	Channel Definition Format (CDF) is the proposed open industry standard for data definition of content to be pushed across the Internet. CDF is an application of XML, which is a subset of SGML, that specifies how data can be automatically broadcast from any web server to compatible receiver programs on client computers requesting such broadcasts.
CGI	Common Gateway Interface A convention for servers to communicate with local applications. Gateways are programs which handle information requests and return the appropriate document or generate a document on the fly. Servers can display information which is not readable by the client, such as a database, and act as a "mediator" between the two to produce something which browsers can display.
CGI input	Data generated by environment variables and standard input (when using the POST method). These environment variables are set when the server executes the gateway program. For example, the environment variable QUERY_STRING represents a string that follows the question mark in the URL. This information could be added either by an isindex document, or by a form using the GET method. In the POST method, form data are read from standard input. Since the server does send an EOF at the end of the data, the environment variable CONTENT_LENGTH is included to determine how much data to read from stdin.
CGI Libraries	A collection of libraries used for writing scripts. cgi-lib.pl is simple Perl library which is designed to make writing CGI scripts in Perl easy. The CGI.pm Perl 5 library uses objects to create Web fill-out forms on the fly and to parse their contents. It is similar to cgi-lib.pl in some respects. It provides a simple interface for parsing and interpreting query strings passed to CGI scripts. However, it also offers a rich set of functions for creating fill-out forms. Instead of remembering the syntax for HTML form elements, you just make a series of Perl function calls. An important fringe benefit of this is that the value of the previous query is used to initialize the form, so that the state of the form is preserved from invocation to invocation.
CGI output	The results of executing a CGI script. The results are either sent to standard output, or by outputting the location of the result document (either a full URL or a local virtual path). The script sends its output to stdout: either a document generated by the script, or instructions to the server for retrieving the desired output. The back-end returns its results to the server as a data stream. The server is responsible for "packaging" the data stream according to HTTP, and for using HTTP to transport the data stream to the requesting client. The server normally adds the needed HTTP headers to the back-end's results.
Chat	Chat software provides the ability to "talk" using your keyboard in real-time with other people on a network of computers like the Internet or a company Intranet.
Checkbox	A field on a form which, when selected, enters a check in the box. These form input tags are best used to select members of small sets.
Chop	A Perl function that chops off the last character of a string and returns the character chopped; primarily to remove the newline from the end of an input record.
Client Headers	Data received from the browser by a CGI script. The header lines are placed into the environment with the prefix HTTP_ followed by the header name. Any - characters in the header name are changed to _ characters. The server may exclude any headers which it has already processed, such as Authorization, Content-type, and Content-length. If necessary, the server may choose to exclude any or all of these headers if including them would exceed any system environment limits.
Client-side imagemaps	A graphic with sub-areas that are linked to different URLs. The MAP that relates parts of the image to different URLs is stored in the current file. This saves a round trip to the server, and should display pages faster. Destination URLs can be displayed in the browser status line as the mouse selects portions of the imagemap.
Cookies	A general mechanism which server side connections (such as CGI scripts) can use to both store and retrieve information on the client side of the connection. The addition of a simple, persistent, client-side state significantly extends the capabilities of Web-based client/server applications.
Color	Colors can be specified in HTML using their names or hexadecimal RGB codes. There are 16 widely known color names: Aqua #00FFFF Black #000000 Blue #0000FF Fuchsia #FF00FF Gray #808080 Green #008000 Lime #00FF00 Maroon #800000 Navy #000080 Olive #808000 Purple #800080 Red #FF0000 Silver #C0C0C0 Teal #008080 Yellow #FFFF00 and White, #FFFFFF. These colors were originally picked as being the standard 16 colors supported with the Windows VGA palette. The above gives the RGB values in hex (#RRGGBB).
CSS	Cascading Style Sheets A mechanism that allows authors and readers to attach the same style (e.g. fonts, colors and spacing) to multiple HTML documents. The CSS language is human readable and writable, and expresses style in common desktop publishing terminology. One of the fundamental features of CSS is that style sheets cascade; authors can attach a preferred style sheet, while the reader may have a personal style sheet to adjust for human or technological handicaps.