Address url for images is this
I've uploaded 3 images in admin thumbnail, small image and base image. None of the images I've uploaded is 400x400.
I can see that its cached, how can I stop the cache setting to 400x400
Go to the admin panel -> System -> Configuration -> ADVANCED -> Developer -> Debug -> Template Path Hints and select Yes (before this you have to change Current Configuration Scope to your website). Don't forget to fill in your IP in Developer Client Restrictions. After this refresh your cache. Then open your product list and see which template is used (most probably it's something like this: template/catalog/product/list.phtml). In this file search for
resize (most probably it will be
resize(400)) and change it to