Seen on Wicket 1.5.3.
If a relative url of a link starts with a path segment containing a colon then the whole uri will be regarded as absolute uri, so typically browsers will complain that there is no handle for the protocol foo in foo:bar/dee/per.
See also the attached quickstart. The start page contains three links, one relative with colon, one absolute and one to a mounted page without colon for comparison.
The application also has a static switch to add an extended urlrenderer, prepending "./" if needed. This fix is merely a quick shot and there might be better alternatives.