It depends on a) what shield in avast is blocking it (?) and b) if it is actually infected or not.
If it is the network shield blocks malicious URLs and there is no user input to exclude a URL considered malicious. You can report it as possibly an FP for further analysis send an email to email@example.com with false positive - network shield in the Subject and full information in the email body.
If it is the web shield, it is possible to exclude a URL in its expert settings, this however shouldn't be done without being 100% clear it isn't infected or the site hacked. Sites being hacked are one of the most common methods of internet infections, so what might be a legit site can get hacked.
So effectively we need to know the URL changing the http part to hXXp so the link isn't active ?