Making a PNG semi-transparent with alpha channel

[anarchoi]

Hi, i desesperatly need to know how to make a PNG semi-transparent (50% opacity), with any program...

I want to see through the tables of my website, and i know it is possible with PNG images.

 

[TeviH]

You're working semi-backwards, I think. Make an image with semi-transparency, say, in photoshop, and thensave for the web as a PNG that can handle transparency.

I use it on my site, www.headlinercreative.com. The black gradient is the same skinny image repeated-y on every page. The stripes are a small square tiled on a layer below it, so the color shows through the gradient.