Mouseover Button Creation - I must be doing something wrong?

Hi All,

I'm trying to create my own button for a part of my website. I've read the help guide, I've tried following the video on mouseover layers but it's just not working for me... so I must be missing something/doing something wrong, I just can't figure out what!

So here's what i've done based on following the video.
1 - created the original size and shape of the button
2 - copy and paste in place the original size and shape of button [changing colour of it for layer effect]
3 - select 'new layer' and give new layer a name
4 - Go back to mouse off layer, select original button and under the web properties/mouse over layer I select the new layer 'description button' in the show pop up layer section.*

* when i've done these in the past I've learned that I have to follow step 4 above in the actual mouse over as we well as the mouse off layer otherwise it won't work but in this time... it's just not working for me.

so what am I missing/forgotten/doing wrong? I've not created 'buttons' before, just pop up layers and mouseover effects for photos... is it different for simple buttons?