Single vs Double quotes (' vs ")

I've always used single quotes when writing my HTML by hand. I work with a lot of rendered HTML which always uses double quotes. This allows me to determine if the HTML was written by hand or generated. Is this a good idea?

What is the difference between the two? I know they both work and are supported by all modern browsers but is there a real difference where one is actually better than the other in different situations?

The w3 org said:

By default, SGML requires that all attribute values be delimited using either double quotation marks (ASCII decimal 34) or single quotation marks (ASCII decimal 39). Single quote marks can be included within the attribute value when the value is delimited by double quote marks, and vice versa. Authors may also use numeric character references to represent double quotes (") and single quotes ('). For double quotes authors can also use the character entity reference ".

So... seems to be no difference. Only depends on your style.

I use " as a top-tier and ' as a second tier, as I imagine most people do. For example

<a href="#" onclick="alert('Clicked!');">Click Me!</a>

In that example, you must use both, it is unavoidable.