Barclays' website appears to have broken for some of its users.
People attempting to use their bank account instead say they are just seeing error codes, with reports of messages reading "error code 6" or just showing "1101".
Barclays' official Twitter account said that the company was "aware of a known issue and we're currently working on a fix to resolve this".
But it also encouraged people to try clearing their cache, cookies and if possible trying a separate browser.
And it said that people experiencing problems with the website should try using telephone banking or its mobile app, which the bank claimed should still be working.
The bank's Twitter account has been posting a flurry of apologies and advice as it deals with a number of irritated customers.
"Hey there, to clarify are you referring to online banking? If so; we’re aware of a known issue and we're currently working on a fix to resolve this," one representative post reads. "Can you try clearing your cache cookies and web browser history? Also can you try using a different browser please?"
Barclays' advice appears to suggest that the problem is something to do with how browsers are storing information in their cache. Web browsers will often download data from websites so that they don't need to access it from the internet every time that page is loaded, but if there is a problem with that cache it can cause those websites to stop working properly.
If that is the case, then clearing out the cache – or switching onto a different browser or just into an incognito window – should allow the site to load properly again.
Another post said that Barclays does not know how long the problem will take to fix, but that it was working as quickly as it can.
