.htaccess files

Please can somebody explain this to me. As far as I'm aware, I have a hell of a lot of duplicate content on my site and a great deal of link juice is being wasted on these duplicate pages. for example, my home page has 4 different versions:

www.domain.co.uk
domain.co.uk
domain.co.uk/index.html
www.domain.co.uk/index.html


My deeper pages also seem to have four versions.

domain.co.uk/keyword.html
domain.co.uk/keyword
www.domain.co.uk/keyword.html
www.domain.co.uk/keyword


Does Google and other search engines recognise the different pages as being the same? Or are links being wasted when they're sent to two different versions of the same page.

I know that when people memorise a site's name they very rarely add the index.html or even just the .html. Any linking to my website will be wasted in that case as all my internal site links go to the URL that doesn't get back-linked.


Am I being paranoid here or does this need fixing. A friend of mine mentioned htaccess files but he said he didn't know very much about them. I'm guessing that I need to set a rule here so that all the different version all redirect just to the one I choose.

That way, the internal link juice isn't being wasted and any natural links aren't wasted either. I'm guessing that I need all other possible versions to go to the www.domain.co.uk version.

Do people recommend I do this. Am I missing something blaringly obvious here?

My sites are all either with hostgator or 1and1. Does anybody have any experience doing it themselves and could point me in the right direction for how to actually do this?


Really appreciate any help anybody can give me here. I switched from wordpress a while ago (which seemed to automatically do this for me) and never realised until recently what's happening here.

Thanks in advance for any advice anyone can give me