I have a 12volt 17ah sealed lead acid battery and I want to operate a small 12volt 90ma camera to it. Will I fry this Camera if I

Is there a reason you aren't using an A/C adapter? I'd hardly call that portable.

It won't fry your camera as long as you connect + to + and - to -. The important thing (besides polarity) is the voltage--which matches.

The current ratings simply let you calculate how long this battery can power the camera. In this case:

hours = 17amp-hours / 90 milli-amps
or 17 / 0.090 = 189 hours

Hope this helps,
WallyH