Originally Posted by till
If it affects only some pages and not complete webites, then its most likely not dns related. Have a look in the error.log of the website for detailed error messages.
At website error log is nothing interesting, only lots of
[Mon Sep 01 18:32:58 2008] [error] [client 88.101.xx.xx] File does not exist: /var/www/web1/web/favicon.ico, referer: http://www.mywebsite.tld/
Can it indicate something? But I still think that it is DNS...
And next thing...sometimes only on some websites...is loaded only plain text without styling. Is it different problem or it can be next symptom of that same problem?