The pages - located at vkernel(dot)org, aveonix(dot)org, smolvell(dot)org, stocknick(dot)org - are not able to detect what browser the users use and serve either a Firefox or Chrome themed fake update warning.
...Users are warned to be careful when being presented similar pages. The aforementioned four are still online, but there might be others. In any case, it's always best to update your browser by using the updating mechanism it contains."
More Bogus "browser update" pages deliver malware