The rules listed in Table 15.1 must be respected. Luckily, it is possible to ask Firefox to scan your file, and if there are problems, you will usually get an error message. Make sure the file...

The rules listed in Table 15.1 must be respected. Luckily, it is possible to ask Firefox to scan your file, and if there are problems, you will usually get an error message. Make sure the file extension is .xml and the file contains the mandatory first line, then open it with Firefox. Having removed the tag from Figure 15.1 , Firefox flagged that error with this message:

Table 15.1

Figure 15.1