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A bitmap is a mapped array of pixels that can be saved as a file.
Both JPEG and GIF are bitmap graphic formats. Currently, the only other way to store an image is as a vector graphic. You can’t easily scale bitmap images, but you can control every single pixel and thus achieve many effects impossible in vector graphics. Conversely, vector formats offer advantages of scalability and lower bandwidth requirements. When you compress a bitmapped image, you suck out some of the visual information.
To bypass this, the portable network graphics format (or PNG, pronounced “ping”) was designed to store a single bitmap image for transmittal over computer networks without losing this data.
CPM, or cost per thousand impressions, is the marketing world’s metric for judging the merits of different media buys.
Offline, CPM is calculated by taking the total cost of a given ad buy, dividing it by the total estimated viewership of a given advertisement, and multiplying the total by 1000. Here’s an example: You buy a magazine ad for US $5,000. The magazine’s subscriber base is 50,000. Therefore, the CPM will be ($5,000/50,000) x 1,000, or $100.
On the Web, CPM is a little different. Since it’s so difficult to accurately determine the total number of visitors to a website, the CPM is calculated using the number of actual ads served. The distinction is subtle, but critically important: in the offline world, marketers simply guess how many times an ad is seen, whereas on the Web, we know.
These are the types of media you can include in an HTML page, such as audio files, flash or GIF animations.
The conversation between browsers and servers takes place according to the hypertext transfer protocol, or HTTP.
Written by Tim Berners-Lee, it was first implemented on the web in 1991 as HTTP 0.9. Currently, web browsers and servers support version 1.1 of HTTP. It supports persistent connections, meaning that once a browser connects to a web server, it can receive multiple files through the same connection.