As with all web pages you may get error messages when trying to access an online resource. If you keep getting returned to the same page, the page isn't redirecting properly or is coming up with an invalid response then you may need to clear the cache on your browser. 

Instructions on how to do this for each browser are below:

Google Chrome:
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Open Chrome - and then perform either a) or b) to get to the required page
a) Navigate to chrome://settings/clearBrowserData in the Address Bar - this takes you directly to the required page
b) Select the 3 dot menu in the top right > Settings > Privacy and Security from the left > Privacy and Security - Clear Browsing data

Set 'Time Range' to 'All Time'
Ensure that 'Cookies and other site data' and 'Cached images and files' are checked
Select 'Clear Data'
Close Chrome completely
Open a new Chrome session
Re-attempt the task

Internet Explorer:
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Open Internet Explorer
From the top right, select the 'cog' icon for the menu, and select 'Internet Options'
In the Internet Options window, in the 'Browsing History' section - select 'Delete...'
Ensure that 'Temporary Internet Files and website data' and 'Cookies and Website data' are checked
Select 'Delete'
Close Internet Explorer completely
Open a new Internet Explorer session
Re-attempt the task.

Mozilla Firefox:
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Open Firefox
Navigate to about:preferences#privacy in the Address Bar, to open the 'Privacy and Security' options
In the 'Cookies and Site Data' section - select 'Clear Data'
Ensure that 'Cookies and Site Data' and 'Cached Web Content' are checked, and select 'Clear'
Close Firefox completely
Open a new Firefox session
Re-attempt the task

Microsoft Edge:
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Open Microsoft Edge
Navigate to edge://settings/privacy in the Address Bar, to open the 'Privacy and services' options
In the 'Clear browsing data' section - select 'Choose what to clear'
Set 'Time Range' to 'All Time'
Ensure that (at least) 'Cookies and Other site data' and 'Cached images and files' are checked
Select 'Clear Now'
Close Microsoft Edge completely
Open a new Edge session
Re-attempt the task

Safari (Mac):
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Click on the Safari tab at the top right of your screen and choose Preferences from the dropdown menu.
Click the Advanced tab of the menu that pops up.
At the end of the tab, select the "Show Develop menu in menu bar" box and close the Preferences menu.
Click the Develop tab from the Safari menu at the top of the page.
Click Empty Caches from the dropdown menu.
Close Safari completely
Open a new Safari session
Re-attempt the task