NO! they both are the same its your choice to set it with or without "www" old browsers required "www" but new browsers don't thanks
Just if you use both versions mixed then it can make a difference, better choose one version and stick with that. There was just another thread about similar thing but I can't remember where here.
Yes it can effect your SEO, rankings and PR (not sure about alexa). The reason why it effects your rankings, etc is because http:// and http://www. are 2 different domains (you actually buy 2 domains why buying 1). Bots will also see it like this and because of that you won't get any profit of http:// links when your indexed in google with http://www.
No, they are different. Google treat www.sitename.com and sitename.com as two different domain and therefore you might found they have different PR. To solve this problem, you just need to do the 301 redirect
They are treated as different so you need to choose which one you prefer and then set up a 301 redirect. You can do this by pasting the following code into a .htaccess file and uploading it to the root of your web site: RewriteEngine On RewriteCond %{HTTP_HOST} ^yourdomain.com [NC] RewriteRule ^(.*)$ http://www.yourdomain.com/$1 [L,R=301] Code (markup): The above version will make sure that the www. is always used. If you prefer it the other way around, then move the www. from the Rule to the Cond.
What MartinPrestovic said is the best advice posssible if your server supports htaccess. Many shared hosts still don't provide support for htaccess. In general, if your www serves the same content as the non-www, Google will treat them as the same page. But, if your goal is to squeeze 100% of all the link juice into a single spot, then you should doing what Martin recommends.
Even they both are the same I still recommend you to use only one version. You should choose only one version to build links to it. If you do not careful enough then your built links would be diversified in weights. Example - If you have built 10 links - 5 links to www.domain.com while another 5 pointing to domain.com then your weight will be half split - 10 links to www.domain.com then your website in www version will gain 100% of link weights
For SEO Point of you it really matters my dear : "Canonical Issue" is the term used in SEO technology. www and non www both shows different results. is also effects your PR and SERP Ranking. you can Manage with Webmaster tool or using redirect with your server setting using htaccess file . is depends what u r using linux hosting or windows hosting .as per my experience alexa treat both of them same.............
Now i have redirected the non www to www with the code given by Martin, and also added to in webmaster tools the www site with sitemap besides the non www site with non www sitemap. Is it ok now, to have 2 sitemaps of the same site?
you should submit one sitemap including all URLs and you can then keep amending and resubmitting the same sitemap . but remember one thing include all your url with www if u r submiting your sitemap with www included website.
Ok, Thanks, but it could happen smth wrong if i submit 2 sitemaps with 2 different sites (www and non www)
I change all my sites to www. . I don't like non www. just because of personal feeling. "World Wide Web" without it we don't have this forum ^_^