Photoshop :: Watermarking For Images On Website

I do a lot of watermarking for the images on my website an created an action for that. What I did:

place water mark select both layers align left and bottom move the watermark layer up and to the right with the arrow keys (padding from the side of the picture) 

Before I apply this action to my images I make them all 930 pixels in width with the original ration, so the height varies. When I apply the action to my images, on some of the images the watermark shows up just fine (like I created the action) but on some of them the watermark shows up very small or to large.