The coding of this site contains a very basic mistake whoever wrote the site does again and again.. and again…
Some background: in HTML there are two ways you can identify some part of the page, say the box where you type the departure date: by name and by ID. The difference is that it is legal to give several bits of the page the same name (say, if you had two different forms for booking you could have a box named departure in each of them) but the ID must have a unique value for each element it is used for on the page.
So far so good. Now, incidentally Microsoft decided to extend getElementById a little and let it match NAMEs to under certain circumstances. Guess what – the Eurotunnel page uses lots of elements with a NAME and accesses them with the getElementById function. Consequently everything – absolutely everything – on the page is broken for any browser that isn't MSIE.
Bother. The specification is so nice and logical: getElementsByName finds something with a NAME. To find something with an ID you locate it with getElementById. Perhaps MS and Eurotunnel don't like things that make sense..