Many common XSLT mistakes can often be avoided by using a good XSLT editor. There are several good ones around. Some of them are free. But if you are old school and like to hand code then look out for the following common errors that many programmers make.

Stay away from disable-output-escaping. This is for experienced programmers and even they are reluctant to use it 99 percent of the time. If you're modifying code and see disable-output-escaping being used then you can be sure the author did not know what he was doing. In 2.0 disable-output-escaping it is depreciated and processors no longer support it.

The next common error is using relative paths. The most common mistake is to use an absolute path within a loop. Paths need to be written starting from the context node. This is a must if you want to avoid a lot of errors. Remember relative paths should be preceded with "~/". Another common problem with relative paths happens when including and exporting to Java. When loading as a stream source if you do not set the system ID the processor does not know where the XSLT is and cannot resolve relative paths. By setting the system ID in a stream source you're telling processor where the commonFooter.xslt is located. After this is done double check that you're actually using the right path with your XSLT editor. This is a crucial last step. You'd be surprised how many errors can be eliminated by double checking the path. This is just a good programming habit too.

Everyone makes mistakes with namespaces. There are no easy answers. Make sure your elements are in the right namespace. Understanding that every element has a name which compromises a prefix and that all elements own their namespace node is best. This will help you to understand the various instructions and how they work together in the result tree. This takes care of most problems that arise with namespaces.

It is highly recommended to use an XSLT editor and avoid coding by hand. This alone will cut down on many errors. As mentioned above there are several good ones. Stylus Studio's editor is feature filled. There is also XMLSpy editor. If you want to develop quick error free style sheets than either of these two will do the job.

If you're just starting out Treebeard will fill your needs and it's free.