Opening picture web-links in browser...

Hi,
using 13.1 64bit...
I can not find out where to "change" the default behaviour when handling web-links
html is opened in the default-browser
pictures are opened in the installed picture-viewer
odt is opened in libreoffice instead of browser and giving me a download/saveas popup
and so on, I want all web-urls to open in the browser.
hope you can help me, thanks.