You could indent your code so we can tell what's the child of what.
So you want it to show up - | welpic | weltxt | subscribe | - right?
Since that's also the source order, just float them all left. Then you have to deal with your width math:
#welpic: 460px + 10px (left margin) + 10px (right margin) + 20px (left padding) + 20px (right padding) = 520px
#weltxt: 460px + 10px (left margin) + 10px (right margin) + 20px (left padding) + 20px (right padding) = 520px
#subscribe: 200px + 10px (left margin) + 10px (right margin) + 20px (left padding) + 20px (right padding) = 260px
Total: 520px + 520px + 260px = 1300px
#page (and therefore #mid_content) = 780px width.
1300px > 780px.
Even if you removed all margins and padding and #subscribe, #welpic and #weltxt would STILL amount to 920px, which is also greater than 780px.