Headers

For the Classic Theme, 124px high by about 600-800px wide.

.gif, .jpg and .png are supported, as far as I know.

Thats great thanks.

Hello...I have a problem with Header...I have a image of wide 657px and high 124px, JPG, but when I go to upload the image, there are a error: "Error in the uploader code".

What can I do? 

Can you upload it here to see if it's the admin uploader or the image is the problem?

Yes...

I only can to post the link of the image:

?w=550&h=103

I just downloaded the image, and then uploaded it to my test forum and it loaded OK, see below.

If you had an image there previously (can't see one now) then try clicking the REMOVE IMAGE button and SAVING before you try to upload the new image.

and the person that submitted this photo has a 'guest' account.  Are you having problems logging in?  That may be causing weird behaviors for you.