[GeoNetwork-users] logo

Hi!
can anyone help me?
I would like to change the logo of some of my metadata. I know that it is easy changing the image 21be4069-c516-4190-b8fb-fefff6b69549.gif to the one that I want. But, the problem is that my image is appeared really small. How can i change the width of the html or which is the css or html file that i have to change?

Thanks a lot!