For Opera it worked when i added the following to the .desktop file:
MimeType=...;x-scheme-handler/http;x-scheme-handler/https;
Something similar would propably solve the problem for the other apps.
However, there should be a possibility to set the default app via gconf/dconf. If i change it there the change is reverted when opening gnome-default-application-properties...
For Opera it worked when i added the following to the .desktop file:
MimeType= ...;x-scheme- handler/ http;x- scheme- handler/ https;
Something similar would propably solve the problem for the other apps.
However, there should be a possibility to set the default app via gconf/dconf. If i change it there the change is reverted when opening gnome-default- application- properties. ..