Pls help me

I've added a custom theme to the .info file like this:

name = theme1
description = A blue, tableless, fluid width theme.
core = 6.x
engine = phptemplate
stylesheets[all][] = style.css
regions[left] = Left sidebar
regions[right] = Right sidebar
regions[content_top] = Content top
regions[content_bottom] = Content bottom
regions[header] = Header
regions[subheader] = Sub_header
regions[footer] = Footer

And in my page.tpl.php I've called the region:

I had added blocks in Sub_header region, but i won't getting that blocks.
I am getting the region but not getting the block inside that.
Can anyone point out what I've done wrong?

Thanks.