Hi, Magdalena.
We have been experiencing automated bot attacks on our servers. Our administrators are working on blocking this activity while affecting as few of our users as possible.
We just removed more of the restrictions at 7 a.m. PST. Let us know if you are still having problems.
It is worth noting that our mirrors Euro (
http://genome-euro.ucsc.edu/) and Asia (
https://genome-asia.ucsc.edu/) are usually still accessible when our primary site has issues.
We apologize for the inconvenience as we resolve this issue.