Trello is the central hub for your website project. This is where you will upload anything that is required for inclusion in your website, e.g. text and images (logo files, product images, business images).
You have probably experienced email strings where the original email was about one thing and the final reply is related to something completely different. This is not the best way to manage a project with many moving parts.
Each component of your website project has a Trello card. You can see the option to leave a comment and if you have a look at the little icons in the comment box you even have the ability to @ mention people (like on Facebook) to make sure they receive an email notification of your comment.
Following is a short 5 minute video on using Trello
http://youtu.be/wZR4PLDHzKo
Additionally we use a service called TrackDuck https://trackduck.com. This will allow you to leave comments directly on website design mockups as well as the live website when it is made available for your review.