Site is locking up Safari

This site locks up Safari. Can't use any other open tab until I close this one.
The progress bar fills up halfway, but no more than that.

https://www.portaldasfinancas.gov.pt/pt/inicio.action

Can someone test it for me, so that I know if the problem is only happening on my system?
It worked fine a few months, but it's been acting up for more than a month now...
This is a very important site for me, it's been a major annoyance not being able to use it.

I'm using Safari v7.1.

Thanks in advance.

Thanks!

Maybe it will get solved in some future update...
I don't like to have more than one browser installed, but in this case I'll have to.

Thanks for the replies.

Indeed, the "having only one browser" is something I decided to do without a real reason.
I'll install Chrome. Hopefully, I will be able to use that particular page without problems.