Hi,
When working in Photoshop if I have a couple of layers I merge layers before saving the jpeg.
What does Flatten Image do please
Eddie

Flatten image is basically the quick way of merging all the layers together using what you see on the screen as what comes out at the end.  This avoids the problem sometimes of the image changing slightly depending on what order you merge the layers together.

Hope that helps (and as far as i know it is correct )

Hi inshaala,

Yes that was very helpful. I had noticed a couple of strange things when I have stitched together some panorama's so that may well be the answer.Thank you.
Eddie 

You can also merge visible layers, and mergine doesn't neccessarily flatten the image. The people at Adobe sure love to give us options!

Well, I never knew that!!!  so technically speaking, which is the best method to use on photographs - for instance if I have a couple of layers with text on, one for the frame etc., which would be the best option to get the most accurate end result?

Always keep your Photoshop file with all of it's layers intact. If you use Save for the Web, it will automatically flatten things for you. If you are saving it for high end printing, Flatten the whole thing.

what Kort said

OK - pretty much what I did anyway except I usually merge visible rather than flatten - but I'll use the flatten option from now on.
I usually save the layers as a PSD first anyway, just in case I want to go back and make any changes afterwards.
Thanks for the advice and thanks ejn for asking the question!! xx

Another big thanks for the replies 
Eddie

one other point to add is that extra layers will increase the file size so if you dont save for web as Kort says the file may be bigger that expected..