There is no error in Blockchain, and you have mis-titled the content of your question, as it is completely irrelevant, I hope you don't rush into making something, especially in creating discussion topics.

I just tried the site you mentioned, and it worked for me. However, if you still can't use it and want to use an online Bitcoin calculator, you might try other sites like Coinmarketcap, Coingecko, Coinpaprika, and others. For your reference, you might want to check out or try the following sites for your Bitcoin calculations, I hope it helps you : Bitcoin.com - Bitcoin

Personally, I still often use coinmarketcap for Bitcoin calculations, because it seems more user friendly to me, here it is: Coinmarketcap.com - Bitcoin

By the way, what calculations are you referring to? Are you looking at the historical value of Bitcoin? Or are you looking to calculate it against Fiat, or vice versa?