I know there are several ways but what is the best way to compress your signatures under the 70 kb without losing to much quality. (and dont want the white border in a jpeg??)

Saving them as jpeg instead of png would be a start
If it's still too big as a jpeg, you can lower the quality if you use Photoshop (file -> save for web/devices)
If you're referring to your sig with the white border, that would be because whoever made it gave it a border and the only way to take it off would be to either crop it out or open the psd file and remove that layer

Avoid using a large amount of colors and transparencies. Utilize the jpeg compression. 60% is usually good for small images on here (if using PS).

Okee i can make it smaller now and i've seen that the compression is good. But if i got a transparant signature, it makes everything on the back white instead of being transparant, how can i avoid that? it only works if i safe as a .bmp but that makes everything to big again ?

Save it as PNG
If it's too big, use less color or use a posterize layer, or both