WHAT ARE ON-SITE SEO AND ON-PAGE SEO?
On-Page SEO is the optimization of the elements of an HTML page for Google search. This typically includes content and tagging. On-Site SEO includes On-Page SEO as well as the optimization of site elements that are not confined to a single page, such as site navigation and hyperlinking, sitemaps, Robots.txt, some coding choices, etc. (On-Site SEO is distinguished from off-site SEO, not covered in this post, which has to do with promoting your website on other sites.)
On-Page and On-Site SEO are important to your site's search friendliness. Basically, your these elements form a kind of search engine oriented resumé for your site and your business: they tell Google and the rest of them what your site is about, what subjects it’s most relevant to.
GENERAL ON-SITE SEO FACTORS
Site Quality. That is the SEO requirement number one in serious SEO today. Make a site that users love. Make one that they love more than your competition’s. Google measures user behavior and knows whose site is better for which search.
Content. The cliché that "content is the king" has never been truer than now. Your website must provide authentic, useful, unique content that stands out from the rest and also has the markings of authority and trustworthiness. Try to provide unique value to your visitors and help solve real life problems in special ways. Create multimedia content, including video, images, infographics. Make sure that all your important pages have substantive text content as well. You may want to keep the top of the page spare and focused, but add content below.
Killer User Experience. Make sure that the site navigation is easy to understand for a normal visitor. Also the site should load quickly both on desktops and mobiles.
Domain Name. Get the best domain name you can find or afford. Whether you have keywords in it or not (there are potential pros and cons to either approach), do not use a sucky domain name. Having keywords in your domain can help a bit. Additionally, having an exact match domain name can still give you a strong boost on Google (and other search engines) for that keyword, often up to #1-3, though it’s not guaranteed (and Google has reduced the power of exact match domain names for "low quality sites.")
Site Structure, Navigation, URLs. The best solution is a flat site structure, with short navigation toward all your important pages. Make navigation easy and intuitive. Use text linking, or make sure to use meaningful Alt-tags if you use graphics for buttons. Your most important pages, such as your product categories, for example, should be linked directly from your home page or from your top-level site-wide navigation. Ideally, nothing of importance should be more than two clicks away from the home page. Minimize the number of slashes / subfolders in URLs. URLs should be flat, transparent, search- and user-friendly. Google had admitted that using keywords in URLs helps SEO a little bit. Do not use more than a few keywords though, keep your URLs reasonably short. Avoid parametrized dynamic URLs or any ugly-looking URLs. On Unix, use mod_rewrite to make nice URLs.)
Duplicalte Content; and URL Canonicalization. Do not needlessly duplicate content across your site; minimize the amount of duplicate content. When duplicate or highly similar content must appear on different URLs for any legitimate reason (for example, you may be testing a different version of a page, a different design, or you may have different versions of the same page in AdWords). You can either block Googlebot from the secondary pages and duplicates, or – a less extreme measure that I recommend – use canonical links on the secondary version of the page. (Example: <link href="URL of the canonical page goes here" rel="canonical"> -- and it is OK to include the same link on the canonical page and having it refer to itself; in case you are worried, this causes no issues.) Decide whether want your site to appear as example.com or www .example.com, and then canonicalize all the URLs accordingly. Use only the preferred form of the URL in all links.
Crawlability and Indexability. Make your important pages accessible to Googlebot and the other search bots. Use Robots.txt or Meta Robots tags carefully if you want to restrict search engines from accessing some of your pages. Make sure that there are no errors that can prevent search bots from correctly crawling and accessing your pages. Do not replace text with graphics or flash. (Read more about crawlability in this sticky: forums.seochat.com/google-optimization-7/google-crawling-indexation-101-a-324216.html )
Cross-Platform Compatibility. Today people use multiple devices and different browsers. Optimize your site effectively to work well on all platforms and across all major Browser versions. Including, alas, that old piece of junk, Internet Explorer 6 – sorry, guys, that’s still 5% of the total user share.
Internal Links. Proper internal linking helps your SEO, site architecture, and richer user experience. Have a good clean internal linking architecture, but also make sure to have a lot of contextual interlinking in relevant content. It is fine and helpful to use relevant keywords in your links. Use your links to drive the ample flow of link juice to all the important pages that you wish to rank. Link juice should spread freely throughout your site.
Outbound Links. If you have an established domain, do not be in a rush to switch to a new one. Do not allow any link building on your site; if you allow users to post links of any kind, it is best of all to nofollow them if you have no control over where they are going. Also, be aware that outbound links can bleed Google Page Rank from your pages. I believe in linking only to relevant and authoritative sites. Do not link to bad neighborhoods or to anything that is of low quality.
Broken Links, 404 Pages, Deleting Content. Fix all the broken links on your site. For example, download Xenu Link Sleuth (free) and run it on your site. Also, make sure any missing pages do not result in 404 errors. When removing content, implement a 301 redirect to the most relevant URL or (unless you can't find a better page) to the home page.
Monitoring and Best Practices. Though these are not ranking factors, they deserve mention here. Monitor your site’s traffic and check it for technical issues. Use Google Webmaster Tools data and Analytics. You can only troubleshoot when you know what to troubleshoot, and that’s how you find out. Create an XML sitemap and submit it to the search engines via their respective webmaster tools. If you have videos, create and submit a video sitemap.
Social Sharing Buttons. Social Media plays an essetial role in your SEO and online marketing activities today. Place social buttons on your site pages.
ON-PAGE SEO FACTORS
Title Tag. It is the most important on-page SEO factor. When search bots index your page, the <title> tag is the first thing they look at. It tells them what the page is about. On your Home page, write a Title Tag that represents the overall theme of the website and looks good to your visitors as well. A perfect Title tag should contain the most important keywords closest to the beginning. Many recommend mentioning your brand at the end of the title tag.
Keywords in Content. You should have your keywords used in your content naturally and meaningfully. Google warns that spammy "keyword stuffing" can be a negative ranking factor. It is probably more true that it won't help you much at all, and will also cause more of your visitors to leave (which can indeed drag down your rankings if your bounce rate skyrockets). Write for people and not for search engines. Do not repeat your keywords in the content unnecessarily.
Meta Description Tag. Including keywords in your meta description does not influence your search rankings. You want a meta description that will make your prospects click on your link in the search results, because your clickthrough rate (CRT) has SEO importance. Think of your meta description as an ad. Include your unique selling proposition, or one or two top selling points most relevant to the given page.
Heading Tags. Keywords in HTML heading tags, such as <h1>, <h2>, etc, do not make for a powerful ranking factor on Google, but they can help somewhat, especially for the less competitive and "long tail" keywords. The most important heading tag is <h1> and the power of the rest of them, from <h2> to <h6> is insignificant. Do not use multiple <h1> headings on the same page unless your content is really ample and justifies it. I do not recommend using <h3> and beyond: they create clutter and betray the expectations of the majority of Web users.
Image Alt Attribute. The HTML Alt attribute used to describe images on a webpage. It is recommended to optimize the images on your webpage and use relevant keywords there. Well optimized images can also appear in Google Image results and drive additional traffic to your website. Additionally, keywords in the Alt attribute on image links take on a special importance: you can think of them as being similar to link anchor text.
Rich Snippets. Use rich snippet markup code to let Google better differentiate and interpret your content. This is a big topic I will not get into here, but useful info can be found at searchengineland.com/from-microdata-schema-to-rich-snippets-markup-for-the-advanced-seo-162902 .
OBSOLETE AND FALSE ON-PAGE FACTORS: DO NOT SWEAT THESE
In old sources concerning on-page SEO, you may run into mention of the following obsolete or false on-page SEO factors. Ignore them, do not waste your time on them:
• Meta Keywords Tag. It looks like this: <meta name="keywords" content="keyword1, keyword2, keyword3">. This tag is code clutter and also tells your competitors what keywords you are targeting. Ignore it.
• Meta Title Tag. Unless the important <title> tag, the meta title tag looks like this: <meta name="title" etc> is obsolete, do not use it.
• Bold/Strong and Italic/Emphasis Tags; Font Size; Font Color. Today these have only presentation value and no SEO value. Use them in a way that best serves the user.
• Keyword Density. Do not worry about keyword density. It is a myth that the major search engines have ever used it as a ranking factor.
• W3C Validation; HTML5. As a techie, I think W3C Validation and HTML5 are totally cool. However, they don’t help your site rank better. Nevertheless, clean, compliant HTML is the basis of good cross-browser performance and thus indirectly relevant to user behavior and hence SEO.
SEO experts, I have tired to be thorough, if you feel something is missing from this account, please comment below, and I will update this post.
When quoting from this post please refer to the source.