Mark, The question is what do you expect as basic knowledge from your audience ? Perhaps it would be good to add a list of references/index at the top/side/bottom of your page where a reader can get the basic knowledge. Chime -> explanation and Link to MDL pdf -> explanation etc As you cannot predict the knowledge and intelligence of your clients, there will be always something going wrong. So, might be that explanation links are the easiest way ? best regards Michael -----Original Message----- To sum up the results: most people haven't a clue what a pdb file is. chemweb: A list for Chemical Applications of the Internet. To post to list: mailto:chemweb@ic.ac.uk Archived as: http://www.lists.ic.ac.uk/hypermail/chemweb/ To (un)subscribe, mailto:majordomo@ic.ac.uk the following message; (un)subscribe chemweb List coordinator, Henry Rzepa (mailto:rzepa@ic.ac.uk)