<a href="" disabled="disabled" ...>

is selectable with

    [disabled] { }

or

    [disabled="disabled"] { } 

And

    [disabled]:not(.greyButtonStyle) { } 

does the last example if you classed that style, doesn't it? I've only done a little CSS, not very recent ... unless you're recruiting, then I'm an expert ;o).

I imagine though there are times when you want to class (some) button tags as .button.