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.
Much like an oil painter with her palette of many unique color combinations, each operating system has its own palette. Many computers out there display only 256 colors at a time, and the Macintosh and Windows operating systems reserve about 40 colors out of the 256, leaving 216 available. Netscape Navigator, Microsoft Internet Explorer, and NCSA Mosaic implemented a 216-color palette that won’t dither (i.e., vary the pattern of dots in an image) on different platforms and is “browser safe” (in other words, these 216 colors will always look the same, no matter what platform or browser is being used). Theoretically.
To fill an image means to paint the inside of it with a selected color or pattern.
The fill can be used to create shading and other simple effects. In HTML, a popular technique is to fill tables with colors, especially in long lists of information. For example, if you are making a web page showing the 50 top-grossing movies of the year, it will be easier to read if you fill the rows of the table and alternate the background colors.
The cell is nature’s building block, and the pixel is the web designer’s. Pixel is one of those half-baked half-acronyms:PICture ELement. It refers to how monitors divide the display screen into thousands or millions of individual dots. A pixel is one of those dots. An 8-bit color monitor can display 256 pixels, while a 24-bit color monitor can display more than 16 million. If you design a web graphic on a 24-bit monitor, there’s an excellent chance that many of your 16 million pixels won’t be seen by visitors to your site. Since the agreed-upon lowest common denominator palette for the web has 216 colors, you should design your graphics using 8-bit color.
(see Bit Depth)
Flatten is a function in image-processing programs, such as Adobe Photoshop, to combine multiple layers into one file.
For example, in order to move the file to another program or save it as a GIF or JPEG, you will have to use the flatten function to combine all layers into one.