Depends on the brand, but one hour, or even less is usually considered missed. Just take it as soon as you remember.
An hour late does not mean "missed". You have to take it within a certain time range. Generally if you take it the same day you will be fine, but if it comes to really late in the day and you usually take it in the morning, or it comes to the next day and you havent taken it, then it's considered missed. You usually have a range of time you can take it (a few hours or so).
BLK is more accurate. In order for your pill to be effective, you must take it within +/-2 hours from your normal time. Example... if you normally take it at 9:00 a.m., you can take it as early as 7:00 a.m. or as late as 11:00 a.m. Two hours in each direction. If you are taking the mini-pill you only have one hour in each direction, which is 8:00 a.m. - 10:00 a.m. if you normally take it at 9:00 a.m. This is not a guess, it's a fact.
2 HOURS. You shouldn't take it 2 hours before or 2 hours after your normal time.
I read on the instructions that over 12 hours is considered missed....