Yes, you can coordinate all three without and. This is called asyndetic coordination, which means that there's no overt coordinator present:
Syndetic coordination: A, B, and C
Asyndetic coordination: A, B, C
In your example, the third conjunct contains the adverb then functioning as a connective adjunct:
[ Go to google.com ]A, [ enter miserable failure ]B, [ then click I'm Feeling Lucky ]C.
You could insert the overt coordinator and before C, or before both B and C. But you don't have to.
When there's no overt coordinator, commas are generally required. In the following example, I've omitted what would be the Oxford comma, making the sentence unacceptable:
*Go to google.com, enter miserable failure then click I'm Feeling Lucky.
Compare this to one of the most famous examples of asyndetic coordination:
I came, I saw, I conquered. (contains obligatory comma)
*I came, I saw I conquered. (missing obligatory comma)
If then truly were a coordinator, we'd be able to join three items without an Oxford comma, or pair two items without any commas:
I ate food, then I went to the store. (contains obligatory comma)
*I ate food then I went to the store. (missing obligatory comma)
But we can't, so it's not.
Of course, this sort of coordination isn't always appropriate. In particular, when the conjuncts seem only loosely related (or not related at all!), people are likely to notice how they're put together and call the resulting coordination a "comma splice". To some people, the difference between asyndeton and a comma splice is whether or not they like the result:
I came, I saw, I conquered. (I like it, must be asyndeton.)
??Computer games are fun, I'm hungry. (I don't like it, must be a comma splice!)
So use your own judgment. If you're joining clauses that are only loosely related and you think they need an overt coordinator, put one in. (Or don't coordinate them.)