If hosts file does not seem to work in your browser

Given a host file with the following content:

10.100.12.10 yourhost.co.uk

If your hosts file does not seem to work with yourhost.co.uk when you load that url in firefox, internet explorer, chrome and/ or safari and you get a message like this:

Network Error (dns_unresolved_hostname) 

 
Your requested host "yourhost.co.uk" could not be resolved by DNS.  
 

For assistance, contact your network support team.  

but ping can resolve the ip address,

Pinging yourhost.co.uk [10.100.12.10] with 32 bytes of data:
Reply from 10.100.12.10: bytes=32 time<1ms TTL=64
Reply from 10.100.12.10: bytes=32 time<1ms TTL=64
Reply from 10.100.12.10: bytes=32 time<1ms TTL=64
Reply from 10.100.12.10: bytes=32 time<1ms TTL=64

Ping statistics for 10.100.12.10:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 0ms, Average = 0ms

Try to go to your internet explorer, then "internet options", then click "connections" tab, then click "LAN settings" button. Although you are accessing this internet options through explorer, it affects the other browser as well. Please untick "Automatically detect settings", at least the fixed my problem, it may fix yours.