David, Firstly the thing you need to understand is that guidelines for elderly web development would primarily fall into two areas... accessibility and usability. To research literature on characteristics of the user group I would initially look towards research in both of those fields directly aimed at people in their older years. webaim.org and useit.com have some really useful base research in this matter however if you Google you should find plenty of studies and information (try to keep it as modern as possible, but any statistics will help you greatly). While this will cover the more computer relevant aspects of each user group because you are aiming at researching a specific type of audience (the elderly) who will be considered a "high risk" group in terms of issues which may affect their experience, you should also take the time to read up on medical conditions older people generally suffer which may affect their ability to use computers. The kinds of things you'll want to examine are physical issues (arthritis, visual problems, hearing problems, motor skill impairments, etc), intellectual issues (perhaps education may be an issue, memory will be an issue, etc), emotional issues (stuff like OCD, psychological disorders, attention disorders, anger issues... all can affect the user) and social issues (like shyness or lack of interaction). Learn the basics about each condition and talk about how all of the various issues (no matter how minor) could damage the ability to use a website or application - the great thing about health issues are their pretty straight forward and can really help boost the overall studies reach.
I don't actually think there's many frameworks explicitly aimed at a group of individuals so that might be out of the window in respect to older adults, however there are certainly guidelines for development of websites and web applications (and even laws you can include), check out the WAI (mentioned by someone else) and ensure to look-up ARIA (for web apps), WCAG (for websites), Section 508 (US law), PAS 78 (UK law) and Google for ADA or DDA (disability discrimination legislation) to help you. The laws usually provide general guidelines to making a website accessible for those audiences. As for usability in those areas, there's plenty of usability guidelines out there both online and in book form you can cite. Usability is about making interfaces easier to use so it's exceptionally important for those (like the elderly) who may have problems with day to day activities. Books you may want to look at include Designing Web Usability / Prioritizing Web Usability (Jakob Nielsen) and Don't Make Me Think (Steve Krug). There's also a great book on Accessibility called Web Accessibility (Publisher FriendsOfED). Usability guidelines to examine on the web include those at usability.gov (they have a HUGE PDF full of useful guidelines you can refer to buried in there somewhere). As for conventions used when building websites or interfaces, the book The Design of Sites is probably the best thing going, it's the size of a phone book and has hundreds of patterns (etc). Granted that's a lot of books but I expect you could find them at a library to rent or something - you want a broad spectrum of sources and verified material within your results.
The books don't make me think and Designing web usability have a lot of information about undertaking usability studies and it would help your research to perhaps carry out some of your own tests (the ones on the net like at webaim.org will have some useful data but fresh stuff works well). You would do best to find yourself some older adults perhaps at the university undertaking adult education courses and ask them for some free time to carry out a test - perhaps build some basic designs and test how easy to use they are for that generation of users, highlighting the possible issues which may exist (note this means talking to the individuals and getting them to explain their actions and browsing habits). To evaluate guidelines both ones you undertake and existing research would mean that you analyse your results. The testing you should do would be better suited if you tested sites aimed at all users (rather than the elderly) as the chances are "older people" websites will already have undertaken heavy usability testing to increase the accessibility of the design. Generic websites often yield the best results as mistakes will be plentiful and you'll have more to examine in your results. The main thing you want from your research is to highlight the issues which exist, think about what could be done to overcome them and ensure you highlight existing research to back up your findings. Testing on it's own doesn't prove anything, but research, documentation and testing will.
Hope that's helpful