If you don't know how to resize your sig, don't worry. Resizing your images isn't all that hard. It's very easy to learn. Just gonna drive right into it...
Right click on your sig in Firefox (or your browser, I assume it will be similar), then Properties. Look under "Image Dimensions" it says "450px by 170px"; since your sig is wider than it is tall, we can easily assume that it is then 450px width and 170px height. Knowing this, we can then conform to standards. Doing so in Photoshop is very easy. Here's a cropping guide I made some time back:
You can skip directly to 6 if you want exactly what you have but smaller, or you could follow it from the beginning if you want to trim a bit off of the top, bottom, one side or another, to help reduce pixel dimensions that way. Overall, it's a very easy process.
It's also very easy, even in Microsoft Paint - everyone has that.
There's also a completely free
program called GIMP that everyone on every operating system can get, which is nearly as feature filled as Photoshop, and the process will be fairly similar, and quite easy.
In the end, image resizing is something very easy once you learn how (and you can in seconds!).
As for the file size, this can be done in several different ways. You probably aren't going to go over the file size limit if you're using an image within the size limit that isn't animated. But, there are ways to reduce file size in Photoshop.
If you have a version of Photoshop CS2 or prior, you will have a program called Image Ready, and that's really ideal. If you don't, you're going to open the gif up in Photoshop by going to File > Import > Video Frames to Layers and then just hit okay once you find it. You'll have to type the name manually since it won't let you see a gif file by default, so just go to the directory it's in and type the name & hit okay. It'll slap it in there. Transparency won't work though, so if you need that then Image Ready is really ideal. You can open it in Image Ready then save as a PSD then do what you need to do in Photoshop, or do it right in Image Ready.
One of the things you'll be doing with gifs is either 1) reducing the dimensions, 2) reducing the colors used, 3) making it more "lossy", 4) or removing frames manually. These four things can significantly reduce file size by a very large margin.
I'm going to use Lan's signature as an example here. Here now all I've done is taken it into Image Ready, reduced colors to 128 and made it 15% lossy.
The file size has dropped down to 2.34MB from 3MB. So, 700kb reduction just by doing that. Still not good enough, but that's a step in the right direction.
I see that this image has 118 frames. That's quite a lot and probably not necessary. We can probably cut that down a bit without degrading the animation too much.
Just import it into Photoshop with the Import Video To Layers method I mentioned earlier, but this time check "Limit To Every _ Frames" and use 2-3 in there. We're going to do 2 first.
You'll have to do Window > Animation to get the animation panel to come up at the bottom so you can see. Now go ahead and click play, now you can see that everything is a bit too fast now that we removed so many frames. We're gonna have to fix that.
The animation was on a 0.01 second delay. Let's change that to a 0.1 second delay and try again. Animation looks smooth. Okay.
Let's go ahead and select Save For Web & Devices, select GIF from the drop down. Now we can leave it at 256 colors, bring lossy up to 12% - keep in mind we're working on the clean image, not the one we edited before.
And now the file size is 1.45MB, which is within the limits. Now let's take a look at it, shall we?
Not too bad, right?
So anyways guys, you see, it's not too hard to conform your signatures within the limits we've set. Once we know how to do it, it's all just following the steps, and there we go. Huge size efficiency gains with very little effort. Not bad huh?
Maybe I'll make a more in-depth tutorial later, but that should be good enough to get you guys started!