Microsoft JScript runtime error: Unable to get value of the property 'getElementsByTagName': object is null or undefined
Understood, because the elements aren't actually there yet. So I removed my reference to the .js in the main header and tried to register the .js file when the update panel is changed instead.
This is my problem.
Sorry for the, no doubt, newbish question. I waited to ask until I had shouted at the screen with sufficient vitriol to warrant begging for help!
Thanks and regards.