<span title> vs ALT for keywords

Does it hold the same weight for kw density?

[lavapies]

Hi folks,

I'm optimising a page where I have very few options (for various reasons), and I was hoping that <span title> may come to the rescue as an option for including critical keyphrases.

Anyone know if the this attribute is given the same weight as ALT tags for keyword density purposes. I imagine it does, as it's always visible to the user, but just wanted some thoughts on it.

Thanks