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3.6. Summary

Units and values cover a wide spectrum of areas, from length units to color units to the location of files (such as images). For the most part, units are the one area that user agents get almost totally correct; it's those few little bugs and quirks that get you, though. Interpreting relative URLs incorrectly, for example, has bedeviled many authors, and leads to an over-reliance on absolute URLs. Colors them. Remember the example where links ended up being white on white?That's the sort of thing we want to avoid.

Let's explore this in a little more detail. Assume thefollowing:

/* reader styles */BODY {color: white; background-color: black;}/* author styles */BODY {color: black;}
are another area where user agents almost always do well, except for a few little quirks here and there. The vagaries of length units, however, far from being bugs, are an interesting problem for any author to tackle.

These units all have their advantages and drawbacks, depending on the circumstance in which they're used. We've already seen some of these, and the nuances of such circumstances will be discussed in the rest of the book, beginning with the CSS properties that describe ways to alter the way text is displayed.

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  • You can use the DOM parser to generate the XML for you if you created an object model that is an adapter on top of DOM. Since your object model uses the document object tree, all the information contained in it is actually stored in the tree. The XML parser can take this tree and convert it to XML for you, you can then save this generated XML to a file. So the DOM parser can generate the ApplicationML file for you.
  • There are advantages and disadvantages to using some of the strategies to import and export XML. The complexity of your application data and available system resources are factors that would determine what strategy should be used.

    Client and Server side - Application Servers

    There is one area of unresolved behavior, which is this: if elements overlap each other due to negative margins, which elements are "on top?" You'll note that few of the examples in this section use background colors for all elements. That's because if they did, content might get overwritten by the background color of a following element. The CSS specification does not say what should happen when elements overlap in this manner; instead, it's left up to implementors to decide.

    It has been argued that all foreground content is always shown