This is a simple troubleshooting tip to help resolve occasionally slow or partial page loads, or when a Web page cannot be found.
Users of Safari 5.0.1 or later on Mac (or Windows) may experience issues in which Web pages are slow to load, only partially load, or cannot be found at all. These issues could be related to DNS settings on your machine or your router.
To help solve this issue, try setting up new DNS servers. Popular DNS servers include OpenDNS and Google's DNS, both of which are free. There are also plenty of other third-party DNS options, found with a simple Web search.
For more information on changing your DNS settings, read this Apple knowledge base article.
If the issue persists after changing the DNS settings, you can disable DNS prefetching. Open Terminal (Applications > Utilities). Enter the following in the Terminal window:
defaults write com.apple.safari WebKitDNSPrefetchingEnabled -boolean false
If this resolves your issue, you should begin troubleshooting your router. Be sure you have the latest firmware for the device. If not, update and turn on DNS prefetching using the following command in Terminal:
defaults delete com.apple.safari WebKitDNSPrefetchingEnabled
If the issue returns, you should consider upgrading your router or keeping DNS prefetching turned off.