The dhistory.org site is currently undergoing major renovations.
While this is happening, some resources have been made available in a static form, while some are not available at all.
Sorry about this, but the site is now over 10 years old, and maintenance is a time-consuming business. We'll try to have everything back up as soon as possible.
QueryPic is available in a static form. You can still use it to create and download charts, but you won't be able to save them. Existing charts should be be available and working at their original urls.
The GLAM Workbench provides some other tools for generating these sorts of visualisations. For example: