Please, it would be great if you guys, if you haven't done so already, could post what your mod's skills actually do, rather than only their in-game descriptions, which we can easily see for ourselves when we download the mod. Unlike the vanilla skills, mods don't have wiki support, and thus there's a lot of stuff you can't know about these modded skills unless you're told about them or you search the mod's code yourself. It's rather irritating considering whether or not to add a mod to my next build when I only have the vaguest of ideas of what the skills in that tree actually do, and whether they'd work well with my other planned skills. If you want it to be a surprise, I can understand that, but at least put it in spoiler tags please.
...or do they? http://j-factor.com/dredmorpedia/ (I've added Wind Magic, Clockwork Knight and both of Essence's mods).
Have you visited the site before? You might be caching old files - try holding control and refreshing the page (or pressing F5). If you're using Internet Explorer I highly recommend switching to another browser (e.g. Google Chrome or Firefox). It should work in IE9 but it'll be extremely laggy and the appearance might be a bit off.
Hmm... I've been testing in Firefox without encountering any issues. Is this the exact error message you're receiving? If so, can you try clicking 'Continue' and waiting a bit longer? (This is an issue I'm working on fixing.) (Also I plan on making the progress indicator more robust sometime, so you don't have to sit there and pray it's actually loading.)