You mentioned adblock but do you also have antivirus? Some of them act as proxies and will look something up on the first request. Beyond that there are a million little things that can cause the first lookup to be slow. Overloaded firewall, edge router trying to purge stateful sessions, link duplex mismatches, disk cache enabled and disk being slow, MSS/MTU too high when using a VPN so the OS retrying with a smaller segment tcpdump would show this, initial window size too big microsoft will block this from people tweaking for high throughput. Try viewing the page with curl and see if that is slow. I would just be guessing at this point without knowing everything involved in the setup. If it's a network issue then Wireshark [1] may be able to highlight some issues. Also try another machine on your network and then take that machine to someone elses network like a coffee shop or bookstore that has public wifi.