IP Bans expire in 4 hours.
Thank you piuk. I tried it now and it is expired. So I can access the site again. (But the duration of ban was more than 4 hours. Something like 12 hours or more.)
May I ask what is the reasonable number of requests? I do not want to give reason to ban in the future
.The time is extended if the ip has already been banned previously.
The request limits are shown on the bottom of the api page https://blockchain.info/api