Q: Why can i browse most websites, but not others?

Basically, I am trying to access few websites and when I try opening them it is constantly loading but won't open.. I could access these websites last night, but for some reason they won't load now. There is no error message, but keeps on loading. I use google chrome, but the same problem persists with Safari and Firefox. I have connection to the internet and I can access a majority of other websites at usual speed. When i leave the 'problem' websites loading for some time i can see that after 10 minutes or so the website partially opens but other parts remain blank and thus remains unusable. I cleared all my cookies, history, cache and everything. Reset my modem. Tried browsing the internet for solutions but nothing seems to work and other solutions are too technical for me to understand.

Thanks.