I believe it's a known issue, but I was wondering if there is still no work around this.
In my trigger, sobject.addError always escape my html tags even if I set escape to false. This is really annoying. I would love to make the error message a bit more friendly when a user try to delete an event.
trigger EventTrigger on Event (before delete) {
for (Event item : Trigger.old){
if(item.EndDateTime < System.now() || item.ActivityDate < System.now()){
item.addError('<span color="red"><b>YOU CANNOT DELETE THIS EVENT</b></span>',false);
return;
}
}
}