Hi, I know that duplicate content will affect the SEO of your website, but how will it affect? will your PR decrease? will Google ban you? or Google will just slow you down in increase the PR. Can someone explain to me how to optimize the index page of the website? I heard that (yoursitename.com) is different from (yoursitename.com/index.html) and is considered as duplicate content if their content are the same but how will i optimize the (yoursitename.com) for it is using the index.html, that what i know. Thanks! Thanks!
Will slow down the indexing process close to zero. As for yoursitename.com or yoursitename.com/index.html you don't have to worry about. SE know how to take care of this aspect.
In my experience it depends on the type of duplicate content and severity of duplicate content. What you were mentioning /index.htm vs. / has to do with canonical issues and in my opinion should have less of an effect compared to more serious issues such as having dynamic URL issues (unique session ID's in your URL that creates multiple URLs with the same content) or anything that looks like you may be intentionally spamming (copying content from other websites, providing the same content on different pages of your site, etc.) Last I heard, Google has said they are not penalizing for duplicate content. They claim they just don't assign any value for the additional versions.
Not true, this gives Google 3 pages to index as the home page and can cause canonical issues, now Google should sort this out for itself but its not always the case, make sure your site can only be accesed by either www or not www not both.
If it is really a duplicate content of another site/blog, then there is a huge possibility that your site won't appear on search engines. If it is a re-phrase of the another or let us say, not a totally copy-paste, there would be a less penalty for it.
If someone posts your content on other domains, let's say it's a portion of your content and not a mirror site. Typically that will not draw a penalty, the oldest version of the content and/or the highest pagerank will typically win and the copies will either not show, or rank poorly. Now, if someone from a highly trusted, high PR site posts your content, you might loose your ranking for that page but unlikely affect the other pages on your site.
As far as I know Google will penalize or sometimes ban your website only if you have the same content on multiple pages of your website or external sites. But if some website is copying your content, you can warn that site's webmaster or complain to Google.
I agree with Pixeladd, it's important that Google can only index one version of your home page either the www or non www, a mistake that a lot of sites seem to make. An internal duplicate content issue rather than a web duplicate issue.