A blank page means normally one of these:

• A fatal PHP error which should be noted in the logs
• A server misconfiguration because of a permissions issue or htaccess issues. That is not necessarily in the error log. But maybe in the access log of the server.

Eh no, in this case a blank page is l;ogical since the plug in is not enabled. All the time that d*mned Register Here thing is there which I can not get rit of. That Register thing is pointing to http://www.3dart4u.com/index.php?p=register which does not exist ... well, maybe it does but it's not active since I do not have the plug-in enabled so it is showing a blank page

All official themes have a register page so the link would be correct. The register link only shows if it is enabled actually (unless you see any cached page).

In addition, Zenphoto does list in an html comment the enabled plugins. Your site lists the register user plugin as enabled.

But I have no registering enabled and not looking at a cached page. So how can I disable that register link? Like I said before: the register plug in is not enabled and I have set my page to Public. I think I missed the setting then to remove the Register link?

@sbillard: I indeed see no register plugin enabled in the comments. Actually it seems this is a bug of Garland as the register link shows up on our own demo then as well. The plugin is not enabeld there as well.

@meegja: You will have to manually modify the function footer() within the functions.php of your Garland theme copy to remove the call.

Register user link is fixed on GitHub now.