Thanks for this - will try. However, the images were sized to fit 600 x 600 as that is the size of the 'placeholder' on the web page. I assumed that it would be better for them to be at that size to minimise the amount of rescaling required. Note that the images look absolutely fine on Chrome on the pc, but not in Edge.

I have an autoplay slideshow (see http://www.stokesleyps.org.uk which displays fine on Chrome but appears very pixelated / low resolution on Microsoft Edge and on my mobile phone. Is there a setting I need to change to resolve this?

Thanks