first of all, can you post a screenshot, or some data from a log-file, showing why the webpage was blocked?
as for being able to access the website that is being blocked, you could look in the avast program's settings, to find a setting for excluding the URL, so that it is no longer blocked..
another option is to look in the avast program's "help" file for information about settings for "excluding" a URL, when it is being blocked, so that it will no longer be blocked..
one of the fist things that a computer-user should learn is to look at a program's "settings"-options.. doing that can help to easily resolve "problems"..
there probably is a valid reason for the website's being blocked..