I have a problem opening some websites, and I don't know why. I have Windows XP. Today I have tried to open my bank internet site and it opens their initial web page, but when I try to connect to online banking it throws up the box with "The page cannot be displayed", "please try the following:" (and then I have tried the options suggested, viz clicking on "tools", Internet options, connections, LAN settings, auto detect etc) Still a problem - I can't open the page. Previously I had no problem opening this website.

Check the filter levels on your firewall and AV.

You can try this:
Click Start / Run / type in; cmd/ and at the black command screen type in; ipconfig /flushdns
and/or try:
Start / Run / type in; regsvr32 urlmon.dll
Click OK

You might also try to empty your Temporary Internet Files folder:
Open IE.
Click Tools.
Select Internet Options.
Click the General tab.
Click the Delete Files button.
When the box opens, put a check in Delete All Offline Content.
Click OK.

Also check PC date and time.
Double click the time in the taskbar, to open, and make sure the Time Zone and Daylight Savings settings are also correct.
Some sites block access when you have incorrect time settings.

Also, see if either of these helps:
Error message: The page cannot be displayed
Troubleshooting "Page Cannot Be Displayed" Errors

Thanks for your help. I dud all that you suggested, but am still having problems. Now I'm trying the troubleshooting page, but not getting very far.

Thanks tq1911 - the last link worked, using Microsoft Guided mode. Much obliged for your assistance!

You're welcome, Samtam.
Good to hear you got your problem resolved.
Thanks for posting back, with what worked.