|Upgrade to current HTML standards, but leave the rest as-is.|
My vote is for tweaking, not dumping and starting from scratch.
I'm currently undergoing a 3-month upgrade to my own site after 10 years of stagnation.
My suggestion is to redesign the layout of the site to be more compatible with mobile browsing, but the functionality is fine as it is.
I've come to trust WW because of the lack of advertising and self-promoting links, and the lightning-fast page load time. This has giving WW the reputation that so many other sites want. Don't become like the others and lose what sets this site apart from the rest.
It really is about end-user experience, and for this WW is already tops. I'm sure you guys don't hear enough compliments on the parts of this site which really matter. It's because you make it see so simple it's taken for granted.
I'd be careful about radical change; those who prefer facebook / twitter will use them; they won't use a WebmasterWorld that's pretending to be them. There are useful changes that could be made - and as I'm no longer very active, it's probably not for me to say - but don't throw the baby out with the bathwater.
Webmasterworld is the best of it's kind; don't make it the 100th best of a different kind.
Yeah, I've dug around before now in the HTML behind WebmasterWorld, and it is prehistoric. From an accessibility point of view, it's in serious need of work, as it's almost entirely marked up using tables.
A move to HTML 5 and CSS with serious accessibility consideration would be a good move, though I'd ask you to wait until HTML 5 is finalised.
Update - css, modern light weight html - carefully coded css could offer a couple of options to view the forum.
Everything else - function, policies etc - gradual and careful change is needed - as has been happening over the last 10 years.
Pretty much what dataguy and Quadrille said. Tread carefully. This is a great resource and pretty darned user friendly, IMO.
I pretty much understand about the WW policy on advertising, but some non-intrusive ads would not make me want to leave or read the forum less. Even better would be a convenient way to turn off ads (if you decide to go that way) with a [button].
Webmasterworld is not about slick displays and fancy options. It's about guys like Brett, engine. JD Morgan, Incredibill, Mack and so many, many more who have been willing to help those like me .. with limited technical abilities .. to go from complete dummy to semi-clueless, so long as I'm willing to help myself.
Do what you need to do to make your business profitable without running off the good guys. The folks like me who get much more from the site without contributing as much will be happy to hang around.
While an upgrade to a fully semantic layout would be nice, I can't understand why there is so much inline stuff in the source - such a bandwidth hole and I know bandwidth has always been an issue for Brett.
Use the css include file, Luke! :)