CSS, or cascading stylesheets, allow you to define how web page elements are displayed.
Specific margins or colors can be associated with elements on the web page; Headers and links, for example. When style sheets are applied to a new page, the elements are changed according to the specifications of the style.
Producing images for the web invariably means minimizing the number of colors (and therefore the file size), and the index color system is another step in this squishing process. With a 216-color palette loaded, Photoshop will map an image to those colors when you move it into index color mode. While this helps the compression and allows you to choose bit depth, it also makes the colors dither, or shift numerically, to the palette. One way to compensate for dithering in the index mode is to use a histogram, which is basically a bar graph of each color’s frequency in the image. In most image-processing programs, you can manipulate the histogram and determine how much weight to give certain colors in the resulting palette.
Dynamic HTML (dHTML) is a markup language designed to heighten the interactive browsing experience.
Because dHTML can utilize each action of the user (a mouseclick, a rollover, a keystroke), it provides a rich and transparent way to process this data.
The resolution of an image describes how fine the dots are that make up that image. The more dots, the higher the resolution. A 300 dpi (dots per inch) printer is capable of printing 300 dots in a line 1 inch long. This means it can print 90,000 dots per square inch. When displayed on a monitor, the dots are called pixels. A 640-by-480-pixel screen is capable of displaying 640 distinct dots on each of its 480 lines, or about 300,000 pixels.
Wireless markup language is used to create web pages and applications for the very small, usually monochrome screens of wireless handheld devices. WML is compatible with the wireless application protocol. It is a specialized version of XML and it is sometimes used in conjunction with WMScript to create dynamic content.