The web is made of code. There are all kinds of code, but the most basic kind, and therefore the code that’s sure to be present on all websites, is HTML. So, the search engines primarily use HTML to try and determine what a website is about. This is the other half of the search engines’ battle. (Firstly they must get the information into their search index.) Once they have the info, they have to parse it (look at it) and figure out what the site’s focus or purpose. Then they’ll know when to serve it to their searchers.
HTML tags are many, but the important ones we want to focus on for SEO purposes are header, bold, title and alt tags. You can see them here:
This is a level 1 header
This is a level 2 header
This is a level 3 header
This text is bold Visible Link text
These are the things a search spider looks for on each page to assign it topicality. Many web pages online are not using these tags properly or they may not be using them at all. Not using them at all is like trying to drive nails by hand when you’ve got a hammer sitting next to you. All you have to do is pick it up and it changes your impact by an order of magnitude.
The use of HTML tags is easy to detect. The proper use of them is a bit harder and it’s going to be specific to your marketing niche. For instance, when our Voltmeter tool shows that you’re using all your HTML tags , that’s a good thing, it means you’re using all the correct tools. But it should also be looked at subjectively to determine whether you’re using them correctly for your website’s purpose.
Code to Content Ratio
The search engines prefer pages that are content-rich. One way to automate the detection of a content-rich page is to examine code-to-content ratios. If your web page has 100 characters on it, and 35 of them are user-facing text while 65 of them are HTML code; you have a 53% code-to-content ratio, which is pretty good. I’d consider anything above 30% good. Anything over 50% is great. Pages with a low code-to-content ratio make the user-facing message stand out to search engines. Think of it as boosting your signal-to-noise ratio.
Why do search engines care about this? When a user hits a page they’ll never know the code-to-content ratio, and it’s not like they can tell what a site’s topic is by looking at a single number, so why bother? Generally speaking, low code-to-content websites are going to be easier to crawl. But the main deal is that looking at this number also allows search engines to infer something about the quality of the site. Sites with a low code-to-content ratio load faster and contain a lot of information for the package they’re in. Generally speaking, fast loading sites with lots of informaton are going to be considered of higher quality and will be in a better position to rank well for the terms they are targeting.