For example, if you have an address book document stored in an XML file, created on a Mac, that you would like to share with someone who has a PC, you can simply email them the plain text address book XML document. This cant be done with binary encoded information which is totally platform (and program) dependent.

Another example is web enabling legacy systems. It is very feasible to create a Java web ennoblement application server that simply uses the services provided by the underlying legacy system. Instead of rewriting the legacy system, if the system can be made to communicate results and parameters through XML, the new and old system can work together without throwing away a company's investment in the legacy system.

XML is an open standard

By making the W3C the keeper of the XML standard, it ensures that no one vendor should be able to cause interoperability problems to occur between systems that use the open standard. This should be reassuring to most companies making an investment in this technology, by being vendor neutral, this solution proposes to keep even small companies out of reach of big companies choosing to change the standards on them. For example, if a big company chooses to change the platform at its whim, then most other companies relying on that platform suffer. By keeping all data in XML and using XML in communications protocols, companies can maximize the lifetime of their investment in their products and solutions.

XML is language independent

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CSS Tutorials

CSS Tutorials

Welcome to the CSS Tutorials. In this section we cover Cascading Style Sheets, the powerful supplement to HTML that allows you complete control over the look of your websites. We'll show you how to create Cascading Style Sheets, and some of the cool tricks you can achieve with them.

For Beginners...

Introduction to CSS
This tutorial covers the basics: what are style sheets? How do I make a style sheet? It also shows some of the cool things you can do with style sheets.

CSS Units
A description of all the units that can be used with CSS, including lengths, percentages, colours and URL's.

For Intermediate Users...

Controlling Background Images and Colours
Learn how to use CSS properties to add background images and colour to your Web pages. Lots of neat tricks and examples are included!

Controlling Fonts with CSS
In this tutorial we take a look at how to control the fonts used in your page body text, using the various font properties that can be controlled with style sheets.

Controlling Text Appearance with CSS
This tutorial shows you how to control the layout of your text using the text properties available in CSS, such as line spacing and text alignment.

Making Lists Look Nicer with CSS
You can really go to town with HTML lists when you add a sprinkle of CSS! This tutorial shows you how to make your lists stand out from the crowd.

For Advanced Users...

CSS Positioning
This tutorial teaches you how to use CSS to position images, text, and other elements on your Web pages. Essential reading for anyone who wants to start using CSS for layout.




precisely target a given type of element. Take this, for example:

Figure 10-4

Figure 10-4. Selecting grandchildren only

The first list item in the source is silver because it's thechild of an ordered list that is itself the child of aBODY. The second list item in the source is thechild of an unordered list, so it can't match the rule.Finally, the third list item in the source is a child of an orderedlist, but the OL element is the child of anLI element, so it doesn't match either.inline box model, because replaced elements have this kind of effect.

We can see the operation of vertical alignment more clearly if we have two images, one of which is vertically aligned with a percentage value. The results, shown in Figure 4-43, are dependent on the line-height, which we'll explicitly declare to be 14px:

P {line-height: 14px;}
IMG.up {vertical-align: 50%;}

Web-based apps might themselves rely on another app server to gather information that is presented on the client web browser. Also, you can write Servlets that get information from remote or local databases, XML document repositories and even other Servlets. One good use for web-based apps is to be a wrapper around an app server, so that you can allow your customers to access at least part of the services offered by your app server via a simple web browser. So web-based apps allow you to integrate many components including app servers, and provide access to this information over the web via a simple web browser.

Web-based apps are very deployable, since they don't require special Java VMs to be installed on the client side, or any other special plug ins, if the creator of the web-based app relies solely on HTML. Unfortunately, this can restrict the level of service that can be offered by a web-based app when compared to the functionality offered by custom clients of an app server, but they are a good compromise when it comes to providing web-based access to your information. In fact, in a real world scenario, both a web-based app and app server may be used together, in order to provide your customers access to their information. In an Intranet setting, you might deploy the clients that come with the app server, and in an Internet setting it would be better to deploy a web-based app that sits on top of this app server, and gives your customers (relatively) limited access to their data over the web (via a simple web browser).

Web-based apps and app servers integrate very well, and this is another reason why Java and XML make a powerful combination for developing systems that give your customers access to their information from anywhere, using any browser over the web. In the future, you can imagine various different web-based apps servicing different kinds of clients, e.g. web browsers on desktops, web browsers on PDAs, and web browsers on all kinds of different consumer electronics devices. By keeping your information structured in a pure way (by using XML), and by allowing access to this information through app servers, you can write many different web-based apps that render this information by customizing it uniquely for each different device that is allowed access to this information. This is more a more scalable solution that storing all this information in web pages, even if these web pages are dynamically generated. So you can have one app server that stores all the data in XML format. You can write a web-based app (which sits on top of this app-server) that allows PalmPilots to access this information over the web. You can write another web-based app (that also sits on top of the same app server) that allows conventional web browsers to access this information over the web. XML and Java have the potential to make this truly platform independent and device independent computing a reality.

API Coverage per category

position: absolute; top: 0; bottom: 50%; right: 50%; left: 0;

Since there is no way to know how many ems tall or wide the element will be, there is no way to make a clipping rectangle that ends 1 em to the right, or 1 em below, the content area of the element.

Further compounding the problem is that rect(...) only accepts length units and auto. The addition of percentage units as valid rect(...) values would go a long way toward improving things, and hopefully a future version of CSS will add this capability.