I've got 125 pages in my site and I don't really fancy going through them coverting to XHTML. I might just do it as an interesting exercise sometime (when the dark evenings set in and there's nothing good to watch on the telly).
We're encouraged to convert to XHTML in order to 'future-proof' our web pages. The concept is that tomorrow's browsers will only need to understand one standard code. This would make Browsers more lightweight for use with phones or whatever else might be used to browse the Internet. Pages that contain code straying from the XHTML standard would not display properly.
It's a nice ideal but I can't see it happening in practice. The demand from everyone who uses the Web, and many who write pages for it, is for browsers to be tolerant of 'bad code' in web pages. Most surfers aren't worried what code lies behind a web page so long as the page looks alright in Internet Explorer on their Desktop or Laptop PC.
If Microsoft were to say, "OK, our new browser will work only with correctly written XHTML" then we'd have to sort out our web pages. This seems unlikely though. Also, there is a tendancy for other Browsers to follow suit these days and cater for HTML Standard variations.
I suppose if you want web pages to be compatible with browsing Internet using mobile phones etc then the convertion needs doing. If not, I don't think we need to worry about it too much ...at least not for a good while.
The ideal of creating a standard isn't new. Web pages are supposed to be written to a rigid
W3C HTML standard (more info
here) but many are not. Some pages look different depending on what browser is used.