I don't think this statement is correct. The only condition is when you are using expression then there should be no space between percentage and equal sign like
I'd say this book is not precise in several areas. For example they go into great details writing about URI used in custom tag libraries. They explain that those URI can be absolute, root relative, non-root relative... When perhaps the most important thing about those URI is that they should bu unique. Nothing is written about that. And if you use the real relative path to your library it will hardly be unique. You don't have to use a real path - but the authors don't mention this.
Alexander Kolesnikov<br />Java Web Developer<br />SCJP 1.4, SCWCD 1.4, SCBCD 1.3<br /><a href="http://sundraw.ws" target="_blank" rel="nofollow">Tapestry 5: Building Web Applications</a><br /><a href="http://sundraw.ws/batik.jsp" target="_blank" rel="nofollow">Java Drawing With Apache Batik</a>