Reload the webpage while bypassing the cache

• Hold down the Shift key and click the Reload button with a left click.
• Press Ctrl + F5 or Ctrl + Shift + R (Windows and Linux)
• Press Command + Shift + R (Mac)

Clear the cache and the cookies from sites that cause problems.

Clear the Cache: Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"

Remove Cookies from sites causing problems:

• Tools > Options > Privacy > Cookies: "Show Cookies"

i know it could be cache problem, but the problem is 404 will be back again very often after clear the cache, sometime 30 minis later. So I think it could be firefox's problem because IE9 and Chrome is so far ok.

This is what I would normally say:

A 404 response is from the server. Either something varies in Firefox's request (different cookies? different referrer? different user agent) or in your connection (different IP address?).

Could you check your connection setting? In some cases, "Auto-detect" can cause problems with sites that tie your session to a single IP address.

"3-bar" menu button (or Tools menu) > Options > Advanced > Network mini-tab > "Settings" button

The default is "Use system proxy settings" but you also can try "No proxy" to see whether that makes any difference.

But in your case I see you use an extension named AutoProxy...

I think this error could be from your proxy instead of the site itself. The site runs Apache and when I mess with the URL to generate a 404 error, it doesn't mention a different server or Tengine.

select：No Proxy， and remove autoproxy, still same problem，

How are you accessing the URL? I've been using your link in your original post, which loads directly. Are you going through a search results page?

just for the link i mentioned. some time is OK and some time has 404, do not know why.