The size limitations also include byte size - as it says on the signature creation page your signature has to be under 100,000 bytes as well as less than 500x500 pixels.
You can check your signature size in your browser, or at a website such as checkyourfilesize.
Your current signature image is still over the byte size limit (535,532 bytes) and will likely be disabled again if you don't remove the image.
But here's my number
So call me maybe ♫
ell how do i reduce the byte size?
♫ And I don't want the world to see me
'Cause I don't think that they'd understand
Sometimes changing the file type (for example, changing a png image to a jpeg image) can bring the file size down enough to make it within the limits. Changing the dimensions can also help reduce size.
With gif images it's much harder, as being huge is part of their nature. If you shrink the dimensions, the image becomes distorted, so that's often not a sufficient answer (plus most gif images need to be really tiny to be within the limits). Reducing the quality and cutting the number of frames can sometimes help, but if you don't personally know how to do that, hunting down someone that does can be time-consuming.
My personal suggestion for an oversized image of any kind is to use a thumbnail that's within the limits to link to the full size version. In the case of your signature, you could use a still image from the gif as a link to the animated one.
[url=Link to your gif here][img]Still image[/img][/url]
That way anyone that wants to see the moving image can click the still to see it, and you're still within the limits.
When everything's made to be broken
I just want you to know who I am ♫