The taglib directive declares that the JSP file uses custom tags, names the tag library that defines them, and specifies their tag prefix. You must use a taglib directive before you use the custom tag in a JSP file. You can use more than one taglib directive in a JSP file, but the prefix defined in each must be unique. In JSP 1.0, the method of creating portable custom tags that can be recognized by any servlet engine is not yet defined. Some JSP engines might allow you to create custom tags, but those tags might not be recognized by other JSP engines.
Empty prefixes are illegal.
If you are developing or using custom tags, you cannot use the tag prefixes jsp , jspx , java , javax , servlet , sun , and sunw , as they are reserved by Sun Microsystems. Inc. All rights reserved.