TAKOBOTO

you shouldn't, one should not
美術館で写真を撮ってはいけない。/You shouldn't take picture in the museum.

One must not harass the animals.

You are not allowed to smoke here, because this is a no-smoke area.

You are not allowed to drink alcohol.

It is forbidden to park bicycles here.

Although I told him "You're not allowed to eat salty!" he added a lot of salt in his food.

Please refrain from taking pictures in the museum.

Don't waste any more time responding to that customer.

You shouldn't count on others for help.

Don't leave the door open.

You must not rely too much on appearance.

Don't look to me for any help except in case of emergency.

Don't set your failure down to bad luck.

You shouldn't do things by halves.

- Teacher, is it okay to play here? - No, you cannot .

Gerund form (Ｖて形) + は + いけない
Gerund form (Ｖて形) + は + いけません
Doing that, it cannot work. => You should not do that.

赤毛

This entry has a typo in it. Clearly the "形" is not part of the entry (unless it is completely silent. ) I suspect that the "形" in "Gerund form (Ｖて形)" was made part of the entry by mistake.

Kurt Schmucker

Technically 行けない is as ok as is いけない. But since it is part of a grammatical structure, the "directed walking" aspect of 行 is unpreferable, thus Hiragana-form is found more often.

adnim

...? て形 means te-form, so it doesn't seem to be a typo. Unless I'm missing something here.

ochacha