Why Does My PC Reboot Itself While I Am on Certain Websites?by David Nield
Unexpected computer reboots can be caused by failing components, corrupted software files or virus infections. If you're experiencing restarts whenever you visit a specific list of websites, this narrows down the possible causes -- in this case, something within the website code itself, or the way the browser reacts to it, must be prompting the reboot.
Your PC will reboot if the contents of the website are pushing your computer's components past their limits. Launch Task Manager (right-click or tap and hold on the taskbar to find it) to see the CPU and RAM load on your system -- if these values spike on particular websites, this may be the cause of the issue. This is more likely to be the case if you're using hardware that's more than a few years old, or a limited amount of RAM. A failing power supply unit can also cause a reboot if your PC suddenly requires more power (to view embedded video or an interactive Flash object on a website for example).
Some websites are embedded with viruses and other types of malware which attempt to infect your PC as soon as you visit them. If you cannot view the websites in question in any Web browser, and they aren't mainstream websites known to be trustworthy, this may be the problem. The best way to guard against the issue is to keep your default Web browser and your installed security tools updated with the most recent versions at all times. If you think your computer may have been infected, run a full system scan looking for problems.
It's possible that the site or sites you're trying to visit include problems in the way they are coded -- if they include HTML or embedded objects that your browser is unable to handle, this can cause a PC reboot. This is more likely to be the case if the issue happens on multiple computers and in multiple browsers. Contact the administrators of the site to inform them of the problem and wait for a fix to be applied. In the meantime you'll need to find an alternative source for the information you were trying to access.
Browsers and Extensions
A restart can be caused by a faulty extension or a browser bug reacting badly to something on the Web page you're trying to look at. As a general rule make sure you are running the latest version of your browser and any plug-ins running on top of it. Clearing the temporary data cache and cookies from your browser may also help resolving the issue -- check the documentation supplied with the software if you're unsure about how to do this. Disabling some of the extensions you have installed could also help, particularly if they are directly related to the problematic website (a Twitter enhancement add-on when having problems with the Twitter website, for example).