Search engine optimization is not difficult if you understand the basic concepts. If you know what to do, your website will get the best possible rankings on Google and other important search engines.
The following list will help you to better understand SEO or to explain SEO to your clients:
Four things you should know about link building - Inbound links are very important
The more websites link to your site, the easier it will be to get high rankings on Google. Google considers links to your site as votes for your site. The more votes your website has, the better your rankings will be.
If more pages link to the website of your competitor, then it is likely that your competitor will get better rankings than you on Google. - It is important to get the right links
In addition to the number of links to your website, Google also considers the quality of the links. Links from unrelated websites won't help your search engine rankings as much as links from related websites that deal with a similar topic as your website.
A link from a trusted website that itself has many links pointing to it will help your search engine rankings more than a link from a website with few inbound links. - It is important to keep on link building
Many of your competitors will continue to work on their links. If you don't keep on working on your links, your competitors will pass you in the search engine results sooner or later. - Google doesn't like paid links
Google considers links to your site as editorial votes for its quality. A paid link is not editorial. Google's anti-spam team has asked webmasters to report paid links. If your competitors report your paid links, Google might penalize your website.
Three things you should know about web page optimization - Search engines rank single pages in the search results
You should optimize a single page of your website for a single search term. Do not optimize the same page for more than one search term. It is much better if a web page is highly relevant to one search term than somewhat relevant to many search terms. - Google considers all pages of your website
Although only a single page of your website will be listed in Google's search results for a search term, Google will consider all pages of your website. If you optimize different pages of your website for different keywords that are all related to a certain topic, then Google will think that your website is relevant to this topic and it will be easier to get high rankings for your keywords. - Optimized web page content and inbound links work hand-in-hand
If your website has both optimized content and good inbound links then it will be much easier to get high rankings on Google.
A web page that has been optimized for the search term "green widgets" and that has many links from other web pages that use the term "green widgets" as the link text is much more likely to get a top ranking on Google than a page that only has the inbound links or the optimized content.
Three things you should know about the technical aspects of your website - Redirects can cause problems
Web page redirects have been used by spammers in the past. That is why search engines don't like it much. A 301 redirect is the only server side redirect that search engines interpret as a permanent redirect.
All other redirects (except for a meta refresh redirect in some cases) don't pass the links from the old page to the new page and they might even be interpreted as a spamming attempt. - Search engines don't like duplicate content
Google wants to list only one copy of a piece of content in the search results. If your web page contains the same content as another page on the web then Google will pick one version of the content for their search results.
Google considers exact copies and near copies as duplicate content. Website navigation and boilerplate are usually ignored. Google compares your page's unique content with other pages and if it has a certain similarity to another page than it is considered a duplicate. - You can create duplicate content by mistake
Technically, the URLs Example Web Page, Example Web Page and http://www.example.com/index.php can contain different content. That is why search engines treat them as separate pages.
Only link to one version of these URLs. Otherwise, the other versions might be duplicates of the other.
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Ten things that you should know about search engine optimization (SEO) 
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