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Browsers are software programs that render web pages and help you move through the web.
The browser that triggered the World Wide Web explosion was Mosaic, a public domain graphical user interface (GUI) from the National Center for Supercomputer Applications (NCSA). Released in 1993, Mosaic made it possible to design documents containing images for display over the internet. Up to that point, an internet document was basically just a bunch of text on a server. In 1994, Mosaic ship-jumper Marc Andreessen released Netscape 1.1, following Mosaic’s successful lead, by distributing the browser free of charge on the internet in order to establish a wide user base.
Popular web browsers today include Internet Explorer, Firefox, Safari and Opera. See Browser Charts for information on some of their differences.
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.
x + 10
x < 10
are expressions since they can be evaluated, while
x = 10
is simply a statement
“Impression” is industry parlance for an actual ad viewed.
For example, there’s an ad on this page, so you’ve just accounted for at least one impression. Why thank you! Of course, it’s next to impossible to know if someone actually sees a given advertisement on the Web. After all, a user might not scroll down far enough to see the ad, could be surfing with images turned off, or might press Stop before the ad is fully loaded into the browser window. This can make impression-counting on the web a thorny endeavor, but then the same goes for other media as well (who knows whether people are actually watching the commercial or off in the kitchen getting another beer?). Short of guessing, you’re probably better off slaughtering a goat and examining its entrails.