It isn’t possible to explain why without any information what was the URL, put spaces in the link so it isn’t active, e.g. http: // www . example-website-url.com.
Sites like that, that offers serialkeys, keygenerators, cracks, often contains virus or malware. So it is best to stay away from sites like that to avoid nasty things that came into the computer. It’s also illegal to use stuff like that.
As Bluesman mentions DrWeb doesn’t flag anything for the opening page, but I have my doubts also about keygen and crack/serial sites as you often get a gift that you aren’t expecting. I mean who are you going to complain to when what you are doing is likely to be classed as illegal in many countries.
I also notice on that page there is a link for avast keys, now that directly take income away from Alwil software that provide a free virus solution, free support, etc. etc. so there is no way we could condone that. An alarm goes off for every page that is opened on that site.