I noticed a lot of 404 errors after changing blogging platforms, so I have added a massive tag cloud to my 404 page, so that anyone that followed a link to a category page than no longer exists, will see the tag could.

Will this help sort out my category > tag issue quicker? Will these all be spidered? Or should I (maybe) create a tag page?

e.g. http://www.www.com/articles/category/fitness-gurus
is a 404 as /category/fitness-gurus is now /tag/fitness-gurus

So in theory, someone could scroll down the tag cloud and find the page they were looking for (although I know this is probably unlikely).