Problems loading some web pages
I have 2 problems which have just started occuring when I try to access websites, 400 Bad Request messages and pop up window asking for a user name and password for normally open sites.
An example of the Bad Request message occurs when I go to the Guardian webpage https://www.theguardian.com/travel/2012/jul/11/top-10-pembrokeshire-walks which displays normally but when I try to follow one of the links which should take me to National Trust pages I get the 400 Bad Request message. I have used this website before with no problem but this has started occuring on this and other sites over the last week. I also get the message when I try to go to http://www.nationaltrust.org.uk/main/ from the bookmark I have used for many years.
The other problem occurs when I type www.nationaltrust.org.uk, I get a pop up window which says Authentication required - Mozilla Firefox http://www.nationaltrust.org.uk is requesting your user name and password. The site says: DSL-3782 Usaer name Password.
Cancelling the pop up causes 401 Unauthorised message If I give it any usename and pass word it comes back the the blank pop up again except when I enter my DSL-3782 router username and passwood which gives routers Internet status page with no errors or messages.
I have tried clearing caches etc. with no effect.
These problems also occur on some other websites and on my laptop.
Has anyone had these problems? What is the cure?
There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.
Thank you for the advice. I have since discovered that the problem exists with other devices including iPADs and smart phones, so I think it must be router or ISP problem rather than a PC or Firefox problem. I am awaiting the delivery of a new router which may cure the problem.
Also, have your ISP check your service.