HTML entities I hear you say - what are those? Well, you will almost certainly have used them if you have written any HTML code. They are the little codes that you use to make sure that characters appear correctly when seen in an HTML rendering engine. The most common one you will have come across is probably & - used because the ampersand character does not render in HTML.

Other common ones include " for a quotation mark   for a non-breaking space, and in the UK, the useful £ to make sure that your pound signs appear correctly. They are also really useful when you are writing web pages in other languages - you need them for the French character c cedilla (ç) for instance.

So what use are these to a search engine optimiser then?

Well, the particular one that made me pick up my virtual pen about was &trade; - this renders a trademark sign into HTML thus™. Cool eh? Well yes, but this particular symbol is underused on the web. This is partly because of a certain amount of ignorance of entities themselves - when I visited an HTML Entities list there were ones on there that even I hadn't heard of! Secondly, there are others ways to make this symbol, either just by writing TM or (TM) next to the word, or by using that other HTML tag <sup>. If you haven't come across this before, it is the code for superscript. It renders the letters between the ^and tags above the level of the rest of the letters^{like this}. It is often used for citations or footnotes.

So therefore, you can use either method for marking a trademark

Superscript - this is a trademark^TM

Entity - this is a trademark™

So the size is a little different, but you can adjust that with CSS yes? So why does it matter to a search engine optimiser? The clue comes when you look more closely at the code whilst pretending to be a search engine spider.

For the superscript example the spider sees the code:

        trademark<sup>TM</sup>

Being a spider I'm looking at the words, so I strip out the code, leaving

        trademarkTM

Eeek! Now I don't have the great keyword "trademark" on my webpage I have "trademarkTM" not so helpful!

But using the entity example, I spider the site:

        trademark™

And I strip out the HTML code:

        trademark

Much better: one nice keyword. So now you can see how replacing the <sup> tags with entities helps on the SEO. The astute among you will also have noticed that the amount of code used to render the trademark is also a few less characters, which makes for smaller code which is quicker to download; it's also technically the "right" way to show this code if you want your HTML to be pure.

Additional Note - If I was a search engine engineer I would put a little tweak in my algorithm so that words with ™ or ® next to them would have a little extra weight - as trademarks they are probably relatively important words in terms of page context, similar to if words are bolded. Whether any of the search engines do or not, I have no idea, but it is an interesting speculation to make!