Step 1
Open a new document, with transparent background. 300x300 pixels should be enough and color the background with #cccccc (a light grey). After you have this ready, open a new layer (Layer-> New Layer) and with your Rectangle Tool (U) draw a rectangle. Be sure to make it in the center of the document.
Make a new layer (Layer->New Layer). Now, with your new Layer selected and with your Rectangular Marquee Tool (M) draw a rectangular in the upper part of the white rectangular. Be careful to respect the sizes. Once you have the selection take your Gradient Tool and set like this.
Use #000000 for the dark part and #4f5052 for the light part. Now fill the selection with this gradient color. Should look like this.
Step 3
It's time for a new Layer (Layer->New Layer). Now, again with your new layer selected and with your Rectangular Marquee Tool (M) draw a rectangular in the upper part of the black rectangular. Fill it with and set the opacity to 29%. This you will add a glassy effect to the box.
Step 4
First make a new layer. Then select your Polygonal Lasso Tool (L) and draw a shape just like, at least try to make one that looks like this at the bottom of the box.
Now fill it up with green (#86c55d). Make a new layer and select the upper part of the new green shape, so that we can add a glassy effect. Fill up with white the new selection and set the opacity to 29%.
Step 5
Select the second layer (the one with the white rectangular) and go to Layer->Layer Style->Stroke.
It's tome for some shadows. Go to Layer->Layer Style-> Drop Shadow
Step 6
Make a new layer, and the last, and with your Rectangular Marquee Tool (M) draw a rectangular in the white space of the box, to define the writing area. Go to Layer->Layer Style->Bevel and Emboss and set it like this.
Add some text and the box is finished.
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