Shoot a pm to whoever does the Facebook page (or any other semi-senior volunteer with whom you have a good rapport and contact information) and basically send them exactly the same post you've written here. If you have a list of specific things you'd like to improve and can express that diplomatically (which I have no doubt you can, because you're good at that), it might be worth including those as concrete indicators of what you would like to change.
Most rescues have super awful websites. It's been a pet peeve of mine for months because my rescue's website is terrible and the guy who revamps it keeps making it worse with each new iteration, and instead of updating the pages he just deletes them and puts in new ones with different URLs so all my form letters to adopters get messed up (and of course the guy never tells me when he's changing stuff) and it's just like ARGH WHY WHYYYYYY
sorry, got a little sidetracked there
Anyway: IT people are rare and precious in rescue. Heck, ANY skilled volunteer is rare and precious, but IT people are particularly hard to get. If you have a talent, god knows they need it, and they ought to be jumping in gratitude that you're offering to help with a marketable skill for free.
If they're not, well then, the fault is not yours for offering.
edit: well okay maybe don't call the website "awful" (even if it is), but express that it would be very little trouble for you to do a revamped version and there are specific things you'd like to alter ("X version would be more visually inviting/easier for prospective adopters to navigate because Y reason") but you really don't want to offend anyone who might have worked hard on the current version.
ARCHMX TDCH Pongu the Insane, CD-C, RE, RL1X6, RL2X5, RL3X2 (GSD mix, b. Apr 2010)
Crookytail the Tigerwuff, RL1, ITD (Akita mix, b. Jan 2011)
Last edited by Merciel; 12-11-2013 at 08:38 PM.