Guys, pretty new to JavaScript.

I'm trying to add a "threat con" to a webpage to aggregate current threat levels and security stuff from vatious vendors. I want to add a single graphic from a particular webpage that indicates the internet threat level.

This is the current image:

Problem is, as the threat level changes, the image name changes. Could be threatCon1_ani, threatCon2_ani, threatCon3_ani, or threatCon4_ani.

can anyone share how to go about scripting a check for a file name on another webpage and post graphic 1,2,3, or 4 (or just add the correct SRC= field) to my page depending upon what is returned from the vendor's webpage?