Why not accept em for margin?

[cyberwombat]

It seems the margin parameter for panels is px only. If it's accepted as a CSS string then why not accept em?

[el_chief]

can't be pixel-perfect with ems!

[SunboX]

Pixel aren´t perfect! ;) Sencha uses em´s in its own css files. Think of pixel density:

iPhone 3GS: 163 ppi
iPhone 4: 326 ppi

greetings Sunny