The scary warning from the website alert.policeguardstate.biz is a virus, in fact. This is not any sort of a police warning. This is not related to FBI, GVU, ANSSI or any other law-enforcement agency of any European or world country. In other word, this is a real scam which must be dealt with.
The fake police alert from the site alert.policeguardstate.biz is attacking many PCs these days, primarily in the US and in Europe. You need to know that this scam is run by the pack of cyber frauds who want to get your money into possession. This is how they do it.
First of all, the fake police warning from the site alert.policeguardstate.biz mentions that you've done something really illegal online, this is why your browser has been blocked. Definitely, this isn't true. You've not done anything illegal. This is just the way hackers want to scare you. To make their false claims more persuasive, they add logos and symbols of various police bodies and other law-enforcement agencies of many countries.
This scam from alert.policeguardstate.biz site is indeed a virus that is able to block browsers like Google Chrome, Opera, Safari and Internet Explorer. In order to get rid of this scary message off your PC you must not pay any fine through Ukash, Paysafecard or GreenDot MoneyPak payment systems (as instructed by the crooks). Instead, make sure that you scan your PC with a reliable security software as explained below. Make sure to also reset your browsers that got infected with this scam.