"Do not look out the window!"
Translation:Nicht aus dem Fenster sehen!
wataya already provided a good link for that: http://www.dartmouth.edu/~german/Grammatik/Imperative/Imperativ.html (Look near the end where it says "General directives and recipes often use the infinitive")
The problem with sentences like "Nicht aus dem Fenster sehen" is that they are not "real" sentences, because they lack the finite verb. You basically have to image that there are some omitted words and the real sentence would be:
"[Sie sollen] nicht aus dem Fenster sehen."
"[Sie sollen] bitte nicht rauchen."
"[Sie sollen das Objekt] nicht anfassen."
So the verb "sehen" is at the end, because it is the infinite part of a imperative expressed by "sollen" or "dürfen" or "müssen".
It's something that bothers me often when I see English and German signs next to each other: "Bitte nicht anfassen / Do not touch", because the English version is much more direct and should really be "Fassen Sie das nicht an", which is a real imperative. We Germans are too nice for that kind of direct commands ;)
Oh why oh why did I ever decide to learn to speak German...I think i have cracked it one moment the next I'm thrown into mental turmoil trying to figure out why I went wrong. However I will not quit as I am challenging myself to speak it; if only at intermediate level. Thanks for that explanation, it does help; now keep in touch until I learnt to speak and write it fluently... it may take a while.
'Sehen nicht aus dem Fenster' is wrong, but 'Sehe nicht aus dem Fenster' is wrong, too. You can see the different imperatives here: http://de.wiktionary.org/wiki/sehen_(Konjugation)#Imperativ (First column, 'Präsens aktiv')
wataya provided a nice link above (http://www.dartmouth.edu/~german/Grammatik/Imperative/Imperativ.html) where it explains at the end of the page that "General directives and recipes often use the infinitive", which is the case here, but the infinitive always has to come at the end.
Only if you use the genuine imperative form of the verb. In this case, the (grammatical) infinitive is used to express the (illocutionary) imperative. Here is a nice summary of the possibilites to express commands in German: http://www.dartmouth.edu/~german/Grammatik/Imperative/Imperativ.html