SSL and <html xmlns="http://www.w3.org/1999/xhtml" > tag

This tag is making my https page partially insecure: <html xmlns=“http://www.w3.org/1999/xhtml”>

Just wondering how much the layout and behaviour of the page is going to be affected if I remove:

xmlns="http://www.w3.org/1999/xhtml" 

…or add an ‘s’ to ‘http’?

Its not making your webpage insecure. Browsers don’t use it. Infact stop pretenting to use XHTML and just get rid of it. Just extra meaningless data stuffed into the markup.