how to fix the geometry of the taskbar (xfce-3.8.18) ?

[christine noot-huyghe]

Hello,

I am using xfce-3.8.18. 
Is there a way to fix the size and location of the taskbar, like 
the geometry of the pager ?
 
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|Christine Noot-Huyghe  
christine.noot at laposte.net