I have found that the amrgin wern't set well.
I have changed that but it seams that the left position is not equal to the right. I also found that 20px for Mozilla are shorter that 20px for IExplorer.
Meanwhile i have set
Enought for Mozilla a little bigger for IExplorer.
I also corrected ".editdate"
The bottom has set to -18px wich was fine for a user with one or two possibility (edit, remove, export,etc) but as editors or admin the row of buttons was onto the "created by...."