You upload a website and throw content and backlinks at it. All well and good.
But in the process of assessing your home page you find that the address is displayed variably as
and so on
And for me initially I did not understand what the problem with this was.
Duplicate content. The search engine treat the three examples given above as three different domain names. Three domain names with exactly the same content and layout. Smells of duplicate content to me. Not really great for your search engine optimization
Backlinks. Major problem. You build backlinks to your site. And sometimes you copy and paste the URL and at other times you type it in manually. Problem is instead of getting a ton of back links to one URL, you end up with a bunch to the www domain, some to the non-www domain and others to the /index.html domain. Totally dilutes out your efforts
Is this important. You bet. In fact it is crucial.
Just do a backlink analysis of your own website using the www.domain and then the domain without www. yo could even try the /index.html
You'll find that if you have not canonicalised your domains URL, the results will not make for good viewing
So what should you do now
Decide which version you want as your homepage URL. I tend to go for the www.domain version. This is the version you want Google and the other search engines to index and this is the version that you want your backlinks to point to.
Once you have decided what version you want, do a permanent redirect i.e. a 301 redirect of the other domains to your main domain i.e. the www.domain version
The 301 redirect in my opinion is the best way of handling this problem because it redirects all traffic, human and robot to your desired domain URL
Another option is to use the canonical URL tag. This is a piece of code you put in the header portion of your html code.
The code reads like
<link rel="canonical" ref="http://www.yourdomain.com">
This means that all other formats of the page should be treated as the www version. This is an instruction to the search engine bots and therefore does not impact n human visitors
If you are using Wordpress, canonicalization is easily accomplished. Go to your settings page and type in the version you want as your domain's URL