Originally posted by Mr Skills
If IE has a non-standard way of doing things that means that some IE-supporting sites will not work on Safari/Firefox ... why can't Safari/Firefox just adopt the IE standard?
The World Wide Web Consortium (W3C) spends a lot of time and effort producing open standards and logical ways of structuring "languages" like HTML, XHTML and CSS that are used to create web pages.
Browsers like Firefox and Safari try (not always successfully) to render code in accordance with the standards which means that a designer should be able to predict excatly how his code will look like on a standards-compliant browser.
IE has many quirks and bugs. See this link
for examples of some of the disasters in the IE rendering engine.
However, as you say, it would be possible for all browsers to work towards the (flawed) IE model rather than the W3C standards and so IE-compliant sites would work in their browsers. However, then standards-compliant sites would break instead. Also it would be very difficult for developers of those browsers as they would never have a fixed target of what to aim for as they would have to wait for each version of IE to come out and then fully road-test it to discover all its quirks in order to replicate them in their browser - they would always be a version or two beind and web developers wouldn't have a clue what they were supposed to be developing for. Not an ideal situation for anyone other than MS!
IE is slowly moving towards the standards and is switchable (by use of a doctype in the web page) between a legacy "quirks" mode and a "standards-compliant" mode. However, it is in quirks mode by default and many inexperienced web developers still design their pages by trial and error to work in the IE quirks mode without ever testing them in other standards-compliant browsers.