How to Stop Cookies & Other Devices Hammering Me with Repeated Ads?

Question

While researching this I see many people have many different issues with the various ads we are subjected to while surfing the web, but I could find nothing covering the current annoyance I am experiencing now. My apologies if this is old hat to everyone. I thought it was to me as well until I found deleting the annoying cookies did not solve my problem. It seems the world of online ads has moved on and left me in the dust. I have no gripes with Safari or OS X 10.6.4 which is what I am using. I would just like to better understand this boil on the a** of web browsing, so I might more effectively deal with it.
This is the Reader's Digest Condensed version of the issue. While it's bugging the heck out of me, it doesn't warrant 3 pages of detailed observations and notes. A couple of weeks ago I was interested in a particular type of welding equipment, on a small home-hobby scale. I buy many, many items online. Most all my hobby equipment and supplies I get from online suppliers. What I was looking for was something I was not even sure existed in a small hobby version (a type of spot welding machine). So, I was searching online sellers' stock as well as technical info that might give me a clue to what, if anything, that existed in the scale I desired.
I was searching using the Google bar on Safari 5.0.2. I sometimes found Google's auto completion of my search string to be a bit pushy, but sometimes it was also helpful so I just went with it. For the better part of a day I searched everywhere the browser and Google took me. I visited at least a hundred sites that popped up on my search results pages and / or were linked to a page I visited. I eventually learned there was no viable product out there for me but like most tool nuts I enjoyed the window shopping and even bookmarked some promising sites for another day. Just a typical day browsing the web. I was never directed to any overtly hostile site. I never saw a single pop up ad nor was I ever hijacked to some site I did not wish to visit. Like most, my Safari settings have pop up windows disabled, I only accept cookies from sites I visit, I don't bother with private browsing etc.
OK, the point to all this. Every webpage I see since that day searching for a spot welder, has at least one ad for a welder on it. Most are specifically spot welders but not all. Most come from a Seller named Eastwood. They are an old school autobody repair supplies seller. I don't remember ever visiting their site as I know them well and they don't carry what I was looking for. Now I know this is all normal and I have not described anything close to a malfunction of software or hardware, but that's my issue. I thought it was kind of amusing for a day or two but seeing ads for welders on every single page I load is making me feel a tiny bit exploited. I thought I knew how to fix this. I searched my Cookies for any containing "weld" or "Eastwood." I found a total of about 10 and deleted them and emptied the trash. I figured this would solve the issue. It did not. I see welders everywhere. I feel like a spoof on a horror flick but instead of seeing dead people I'm stuck with seeing welders! Can someone tell me how this persists? Did Google sell me out (and are they still?) Did I just not dig deep enough into the Cookies? Or (and this is my biggest fear) is there some new super sophisticated way of serving these ads to me that bypasses my Cookies altogether? Something I never paid attention when (or if) someone was sounding the alarm? And, no I have never downloaded any questionable extensions, toolbars, helper apps etc. I am well versed in the usual Windows malware and tricks to manipulate someone's browser, it's nothing like that. It's not an evil app trying to take over, it's just a PITA Cookie or ??? that I don't know how or where to find to get rid of it. I hope that's all it is, or that you folks will point me in the right direction of whatever it is.
If anyone has time to explain this a bit and suggest what I might do to stop the ads, I'd greatly appreciate your time and info. And if you ever need welding equipment, I can give you several sites, a minute. Thanks in advance.
Jim

Answer 1

Thanks for the help. Dumping Google cookies seems to have done it. I tried the responses in order and am grateful to Klaus1 also for the Glimmer Blocker suggestion but it was not needed. I wish I understood the "system" better and how Google gets around the only accept cookies from sites I visit setting. Seems Google is the 800 lb. gorilla and can do pretty much as it wishes. Thanks Andy.