isthewebsitedown if you are asking, probably not. if I am asking, probably so

Web Pages Loading Slowly On Vista

Slow web pages under Vista are nothing new. Heck, slow anything on Vista is something you sort of come to expect. But sometimes, you will have just a single machine suddenly get slower, regardless of the browser you are using. This is unusual. If you are running Vista, you may be having a problem with a new security setting.

A recent Microsoft Knowledge base article describes one potential cause of the problem: RFC 1323 compliance. Though the text suggests that it just affects the Enterprise version, the Applies To section lists all versions of Vista. In a nutshell, websites that don’t fully support RFC 1323 or the default Windows Scaling factor of 8 will be very slow or even inaccessible.

There is an easy workaround:

Press the Windows and type cmd, then press CTRL+SHIFT+ENTER to open a command prompt as an administrator. At the command prompt, type:

netsh interface tcp set global autotuninglevel=highlyrestricted

This will set the autotuninglevel to a  somewhat more permissive setting.  If you want to put it back to the default setting, type:

netsh interface tcp set global autotuninglevel=normal

You can disable autotuning altogether with this command,  but do so at your own risk (note that the date on the RFC spec above is 1992. If this was going to get exploited, it would have been done already):

netsh int tcp set global autotuninglevel=disable

It has been asked if this requires a reboot. In my experience, no it hasn't, but YMMV.