Is it legal and ethical to post my notes of a conference I am attending on my website?
Firstly, you will need to ensure that content from the conference is allowed to be shared - I have attended conferences were we were explicitly told not to share the content as much of it was pre-publication.

Secondly, and very importantly, if it is allowed and you do take notes, you should provide proper attribution - referencing the author/speaker and the conference proceedings.

If you are not sure of the legalities of reproducing your notes - ask and receive explicit advice.