Straplines and folds are important.
They are important in life (particularly if you plan any nude sunbathing) and they are doubly important in marketing (where they mean totally different things).
It doesn't matter whether it's a poster, a flier, an advertizing leaflet or even a web site.
You need to get the important stuff above the strapline. Above the fold. With a web site it is good practise not to force your prosepective customer to scroll down too much. People don't like it. It is tiresome. Carpel tunnel syndrome, etc, and all those other health problems that regularly afflict couch potatoes (e.g. swollen right wrists).
Get the exciting stuff up there at the top. Right up where people can see it. All the sexy stuff needs to be there in pole position - the glossy photos, the amazing once-in-a-lifetime prices, the bogof offers, the shiny teeth, the perky ice-cube hardened breasts of your advertizing model (doubly important if the model happens to be female).
People shouldn't have to scroll downwards, or unfold a sheet of A4 to get to the point of what you are trying to sell.
Doubly important is where you place your banner headline.
I cannot stress this enough.
Take a look at the photo above. I scanned this advertizing flier into my computer yesterday exactly as I pulled it from the envelope. It illustrates perfectly the point I am trying to make.
Now. I know what it is supposed to say. Suite Clearance Event.
But that fold... occurring where it does.
When I first saw it, I could have sworn blind the U in suite was an H...
And, yes, when I opened it further I realized that, yes indeed, it should have been an H.
Tits and teeth, people. Tits and teeth.