the JBoss portal reference guide in the chapter 5 (about theme and layouts) says that "left", "center" and "right" are acceptable values for regionName. Are there other values? If so which are?
Effectively, you can use any. All there is to know is that the region you assign a portlet to needs to be present in the layout, otherwise the portlet will not show up on the page.
About the region tag I saw there also is the "orientation" value. Which are the possible values of this var? What is its meaning?
the values are vertical and horizontal per default, but again, you could use any name here. The region tag delegates the creation of the markup to the renderSet. the renderSet (divRenderer, tableRenderer) is the one that can decide to do something with the value of the orientation attribute. In JBP 2.0, the table renderer uses it to produce either a tr or a td for each portlet.
Finally when I put 2 portlets in the same region they are displayed vertically. How can I put them side by side?
As mentioned before, that is the task of the renderSet. You could stay away from tables in the markup , and realize the orientation via css. For that to work, your renderSet needs to create the appropriate markup that the css can use to do its job.
In JBP2.2 the table renderer was removed in favour of the divRenderer. This renderSet however does not value the orientation attribute. Something to think about for me ;)
