Simple Userstyle that removes the warning triangle for attacks longer than 6 hours.
Version 1 keeps the flashing triangle for attacks under 6 hours, Version 2 uses the non flashing variant for attacks under 6 hours.

userstyles.org/styles/133258/ogame-no-attack-alert

Spam attacks longer than 6h won't annoy you, because the red triangle in the top corner isn't flashing the whole time.

Some players asked me for it, so here it is