Joomla CMS will create many duplicate contents in the Google index is not friendly for seo, how to avoid duplicate content? the smiple way is add rel="canonical" tag in the header like <link rel="canonical" href="/url" />, i find a free plugin called MetaGenerator developed by shikle.com that can add rel="canonical" meta tag only for com_content in article, category and section view.
Having a link that looks professional is also an important factor in SEO, your links probably look like this, example.com/5/article. We want it to look like this, example.com/article.
It’s actually not hard to do, we won’t be installing any plugins or modules, just change 2 numbers and comment out a paragraph. Remember it’s always good to make a copy of the file you’re working on, if you do something by mistake, it would be easy to change back.
For the average searcher, these rich snippets help show them what they're searching for is within reach on a particular site. we know Google can display Star Ratings in search results for articles or products that have a review system compatible with Google Rich Snippets.