XML Parsing error

I would appreciate some advice on this warning tag I have received:
XML Parsing Error: mismatched tag. Expected: .
Location: https://www.legislation.gov.uk/ukpga/2006/46/contents
Line Number 76, Column 128:
Similar problems have been discussed before but mine seems to have a unique aspect.
All of my Bookmarks, or URLs shown in searches, work as they should, except one. The UK Government site https://www.legislation.gov.uk/ and subsites return the above copied tag (but I can access it on my Ipad via Safari). I did once reload FIrefox and it worked for a while but the problem has returned. I am software literate but a complete dunce on the technical side. Be kind.
Mike Nason