Images

I have been having great difficulty with having my images seen. It seems i have to make them very very small for the theme to allow them to show. Its a real shame as the whole reason for my site is to have big colourful images on show. If there is something in the preperation for the images i can do please someone let me know. I have been resizing them. i can use photo shop to do this- not that i am an expert on photo shop. I thought that they could be like 2kb and 600 pixels wide. Mine will not show if they are anything like this. Also once I get them in they might be low res but they are also featuring very small