If your net connection is working fine, but your IE browser is displaying 404 pages, it might be time to flush and restart Windows’ DNS cache. In the Command Prompt, type in:
net stop dnscache
net start dnscache
More info can be found at the How-To Geek. Read on…
I also found this helpful tip:
Copy and paste this into the RUN box:
“C:\Program Files\Internet Explorer\iexplore.exe” –extoff
Now IE will open with no add-ons.