How are you saving the jpg file. The one you posted has no color profile, no meta data other then you used CS3 and it is saved at quality 12. Here it is with a color profile and saved at quality 10 is 39KB where your jpeg is 50KB. Again how are you saving with CS3 Save as or save for web and have you tried resetting your Photoshop preferences.
It's the sort of image that JPG would work really well on because it has so little colour.
I have CS5 Version 12.01. I tried "save for web" and that worked for the thing I had to do today, thank goodness!
But I still want to know why ALL of my images are reducing BACKWARDS. It doesn't matter if it's a photo I took myself with my camera (at 300ppi), if it's a .png or .jpg that I've created from an original .psd graphic I created, if it's a photo I downloaded from the Internet like the photo someone took of me and posted to Facebook, or anything else.
Let's say I have bird200x200.jpg, which is 80k. I save it as bird100px00x100.jpg, and make it 100x100. It's now.... 124k. Normally, if you reduce the dimensions it gets SMALLER, not bigger!
JJmack is correct: the larger file size can be explained by the meta data inserted.
As for whether you should embed any colour profile in a jpg for web graphics: I would say "no". (Though I am sure Chris Cox would disagree vehemently ;-)
Png* and gif files cannot have colour profiles embedded (which would throw them off compared to the jpg's in your page), and as a web designer one should strive for colour consistency on a page level, not across different displays. At least in my humble opinion. It's even more important for interface screen design (which is not colour managed at all).
*in Photoshop png files cannot have a colour profile embedded
Btw, for improved jpg quality control, try RIOT instead of Photoshop's Save for the Web tool. It also includes full control of chroma subsampling, which is uncontrollable in Photoshop.