Slow loading of websites is not just because their servers are slow but many a times it is because of the ISP’s DNS settings. To brief DNS is Domain Name resolver which converts the url you type in the address bar into IP address so that it can connect to it faster. This resolving is done by set of servers and faster they do it faster you get to the site.
Name Bench is a free software which can actually bench test your DNS Servers by taking factors like web browser history, tcpdump output, or standardized datasets in order to provide an individualized recommendation.
You can configure for which browser you want to test and then select how many servers you would liek to test on. I would suggest you to lower the count unless you are not in a hurry. Below is the recommendation of DNS server I got after the test was over.
You can download Namebench dns from here and get which is the best dns commendation for your computer.
Related : Change DNS on the go with DNS Jumper