Some sites become unavailable due to maintenance disruptions. As a rule, this problem is quickly solved by the owners of the resources, however, if the portal you need works for everyone else, and you still cannot enter it, then there may be many other reasons.
Find the reason why the sites you need are not opening. If the browser displays an error that the resource is not available, then it is quite possible that at the moment it does not work at all. Ask your friends to go to the site, and if they get the same error, then try to go to the resource later. If a certain number of sites do not open, and instead warnings are opened that they are blocked, most likely you have a virus. First of all, pay attention to the hosts file, which is located in the C: / WINDOWS / System32 / drivers / etc directory. Click on it with the right mouse button and go to the "Open with …" item. In the list that appears, select "Notepad." Look at the contents of the document. The file should contain nothing except the line "127.0.0.1 localhost". If any additional addresses are indicated, then feel free to erase them. Please note that the presence of additional lines indicates the result of the virus. So if you just delete unnecessary information from there, the desired site will start to open, but the virus will not go anywhere. Scan your computer using your antivirus program by selecting the "Full Scan" section in the utility window. If you go to any site it says that your computer is locked and you need to send SMS to unlock it, you can try to bypass it. To do this, using the browser of your mobile phone or another computer, go to the antivirus software website and try the proposed solutions. If the blocking message persists, then use free antivirus programs that do not require installation (for example, AVPTool or CureIt). Run the executable file and select the scan section, after which the program will find the infected files and cure them, and access to the sites will be restored.
