I have done some testing with this and it seems that it is the html editor that is rearranging the attributes in the a tag. In my test I put the value in the same as you and was able to confirm that it is stored correctly in the db when inserted. I then updated the record and checked the source in the editor, the attributes were in a different order than they appeared in the db.
It seems that the html editor is rearranging the attributes when it loads them, it looks to be arranging them alphabetically.
Considering the nature of html tags and the attributes used within them the order of the attributes should not make any difference in the output. It seems that you have confirmed things to be working as they should.