creating own css classes? possible?

[portisheart]

i searched for a faq or help page mentioning it, goggled like mad, didn't find it...
though it's such a basic question ~

is it possible at all to add OWN classes/IDs?? ! IN THE CSS PANEL + ENTRY !
without to touch the layer - only HTML in the entry (i have 1 recurrent div or table i'd like to customize) and a corresponding css block in my sheet. because if i have to write the style inline for every div/table in the entry (a faq), it will fill my entry allowed space in no time, and give me a headache looking at its code.

i tried, it works inline:

blah

but not calling the css with a class, it doesn't work, but i probalbly screwed up - or it's impossible.

in the entry:

blah

and in my css panel (no ext sheet)

.faqGreen {
border: 1px solid green;
background-color: aqua;
color: #221203;
border-radius: 20px;
}

what am i forgetting? or is it sheer impossible on lj?

because when i test it in notepad++, with the style in the header (EXACTLY what LJ does with the css from the customize panel! i can see it in my page's header looking at the source code) - it WORKS.
though, when i look at my page with mozilla's webinspector, and pick this div or table (i tried both), even i can see the css block in my header, no mention of my "faqGreen" formatting on the element itself. i tried !important too btw, no use. as if it had been stripped.. somehow? "inbetween?" makes no sense ~