after upgrading to ubuntu 12.04 lts browser (firefox, chrome) does not load webpages. Connection to the network works and also to the internet (skype is working) Software installaion via sudo apt-get fails ( -5 hostname association ...)
This could be to do with your DNS settings. Are you getting any error messages back from either browser or terminal?
You should pick up your DNS setting from your router/default gateway which in turn picks it up from your ISP. Try editing the connection to use a external DNS. One that I always use is 126.96.36.199 and secondary of 188.8.131.52 which are run by Google. Other options available are OpenDNS.
Ideally this would be some that would be programmed into your router so that your whole network behaves the same other you may have to fix this on each workstation.
Note: This can have issues on your local network if you need to resolve something internally.
I know that this might not be the answer that you're looking for, but since I don't have the outcome of
To manage DNS entries, you can modify DNS names from the
=>Clear all the browser related items like cookies, history and bookmarks.
if first one is not working then follow second.
=>Make an installation of your browser again. remove your existing installed browser.It will help you to cover all those files which are corrupting your browser.