If you're using a proprietary driver for your wireless network card and this card is from Broadcom, you might have experienced an annoying delay when browsing the internet over the ethernet connection (c.f. over network cable). You'll always get it when the browser is looking up the websites, but when using the wifi connection everything is working as expected.
- Go to Administration/Additional Drivers in the gnome menu.
- if you find an activated broadcom network driver here, deactivate it.
Done, your internet experience should be much better now ;)
Note: There are many other solutions around there to solve this problem, but anyhow this was the only one that worked in this case.