Recurring Safari connection error on MacBook Pro

Using MacBook pro

Constantly getting:

Safari can’t open the page “-----" because the server unexpectedly dropped the connection. This sometimes occurs when the server is busy. Wait for a few minutes and then try again.

This is from various websites at different times and on different networks.

I have tried clearing the cache, restarting router etc but made no difference. If I reload the page it connects but invariably a short while later the same thing happens again. This is really frustrating especially if filling in a form as you have to restart all over again.

My wife has a Macbook Air and has the same issue.

Hope there is a solution.

Thanks

Neal

[Re-Titled by Moderator]

Original Title: Safari