The recent backlash against the Gap's rebranding served as a reminder of how effective -- or disastrous -- logos can be. From McDonald's and Nike to Sears and Mercedes, a look at some of the best and worst of all time.

The Gap has found itself in a little marketing hot water, after replacing its longtime logo with a new one that Ad Age described as "something a child created using a clip-art gallery." And that was one of the kinder reviews. After more than 20 years, the emporium of denim, khakis and other casual wear decided to shelve its iconic blue-box-with-white-text logo -- and was immediately slammed across the Internet, even spawning parody Twitteraccounts. To stop the bleeding, the company announced a crowd-sourcing project, inviting consumers to offer alternative logos. The fate of the new logo remains unclear.

It's not the first time a major brand has faced backlash for fixing what may or may not have been broken. Last year, Tropicana was forced to abandon new packaging after a near-universal panning.

Both examples serve as case studies about why logos are such an important part of an overall brand message -- for companies of all sizes. "A logo is some sort of graphic mark, an emblem utilized by many large corporations and organizations to promote public recognition of their firm and products or services," says George Cook, an executive professor of marketing and psychology at the Simon Graduate School of Business at the University of Rochester. "The logo helps the firm initially gain attention and then continue to keep the company and its products or services at the consumers' top of mind when they're in the buying process. Some firms do a magnificent job of this, while other logos leave a lot to be desired."

So what makes a truly effective logo? We rounded up a panel of experts and asked them to share their picks for best and worst.

The Best Company Logos

McDonald's. The key is "memorability," says Walter Guarino, an advertising and branding professor atSeton Hall University and president of SGW, Montville, N.J.-based integrated marketing firm. "If upon seeing the logo once or twice, I can remember it and what it stands for, it's a winner in my book." And those billions and billions of customers McDonald's has served, whose eyes light up at the sight of those Golden Arches, can't be wrong.

Nike. The iconic swoosh is probably the most famous company logo out there, and just for that, it deserves high praise and a place on our list. "Nike's brand essence of 'Just Do It' is captured in its famous swoosh," says Betsy Jordyn, president of Windermere, Fla.-based Accelera Consulting Group, which has worked with numerous Fortune 100 companies, including Walt Disney World. "The name Nike and the swoosh represent the Greek goddess of victory, which is a perfect fit for a company that is the worldleader of sportswear provided to competitive athletes."

Echoing that sentiment is Todd Simmons, executive creative director at Wolff Olins, a branding firm with offices in London, New York and Dubai. "At the risk of stating the obvious, what comes to mind immediately is the Nike swoosh," he says. "Nike taught us all what a traditional logo can do on its own. I like that the logo is abstract and isn't an overt visual translation of Nike, although it has its roots. The swoosh also makes any communication or product better when it's placed on it -- a benchmark for a great symbol."

"The logo is 100 percent effective," raves Ricardo de la Blanca Brigati, CEO of the DLB Group, a multinational advertising company that works with clients including the Cartoon Network and Kraft Foods. "The way the symbol is positioned gives consumers a sense of speed, a quality that obviously reflects the spirit of the company."

Cook notes that Nike "paid a student $35 for their enduring logo. What a buy!" (Years later, as a thank you, Nike CEO Phil Knight gave the same design student an envelope full of stock options.)

The Geico Gecko. The famous insurance lizard is celebrating his 10th anniversary as a spokesman for Geico, and clearly, he and the company are doing something right. As Cook says, the logo is "cute," and the related advertising generally features "humorous stories that we all can relate to and laugh about."

FedEx. What is it about their logo that's so impressive? True, it's been part of the advertising landscape for so long that it's probably hard for a lot of us to see it, but the way Ms. Jordyn explains it, "FedExchanged the shipping industry when it promised its customers 'when it absolutely, positively has to be there overnight.' Its logo communicates this promise with a hidden arrow -- between the 'E' and the 'X' -- which is a symbol of both speed and precision."

You'll be hard pressed to find any marketing executive who will say a bad thing about FedEx's logo. "The use of the negative space to create a subliminal arrow signifying forward motion is brain-brilliant," says Adam Hanft, a branding guru and CEO of Hanfts Projects.

"All-time best in my opinion," echoes Erik Pelton, a top trademark attorney in Arlington, Va.

CBS. Hanft particularly likes this one, noting that the "eye gazes at us from the 1950s with authoritative brilliance and unblinking courage that is all the more relevant right now."

Playboy. "Say what you will," Hanft says. "Marshal the full armamentarium of sexist weaponry. This whimsical masterwork continues to instantly communicate the national value system of Heffnerica."

The Worst Company Logos

Sears. Kelly Day, associate creative director at Bailey Gardiner, a San Diego-based marketing agency, passionately hates the Sears logo. Why? It's confusing. "Not only is their current logo bad, what makes it even worse is that some of their older logos were really, really good," Day says. "Instead of building on its own history and using a logo that relates to its roots as one of the oldest and most-trusted brands, it went generic. It chose a logo that makes it blend in with JCPenney's, Kohl's and all the other large, forgettable department stores. Such a shame."

Coca-Cola. It might seem crazy to knock Coca-Cola's logo -- after all, it's one of the world's most recognizable brands. But the drink has thrived in spite of the logo, not because of it, according to de la Blanca Brigati. "The letters and the red and warm colors are opposite to what the company should stand for." It would have been better, or made more sense, had Coca-Cola adopted something blue, as Pepsidid, which would connote a refreshing, cool drink.

Kellogg's. "This is another extremely successful company that could have a better logo," de la Blanca Brigati says. "The logo doesn't send consumers any sort of message, and it doesn't portray much of what the company stands for. It's not that the logo is bad, but considering the company, it should be much better."

Mercedes. "Yes, it's iconic," Hanft says, "but only because of the car that it adorns. Otherwise, the three-part symbol is cold and remote, communicating no values and tapping into no brain orchestra of emotion."

Edsel. We're reaching back a bit to the infamous car named after Henry Ford's son, which was made between 1958 and 1960, but it has to be mentioned, Guarino says, "because it's among the top of the worst heap. They did nothing right with that car from the start." The logo was particularly awful, he says. "The weird-shaped E with the name of the brand tucked more than halfway down the letter did absolutely nothing to stand out. Occasionally, they used it without the brand name, showing just the 'E' with six hard to count 'em circles around it. I never understand what the circles were for, or why you would take the risk of thinking people would remember the car's name from just the first letter."

Of course, the problem with trying to create a list of bad logos, Guarino says, is that "there are so many forgettable logos out there that it's hard to comment on them."

One of the most frustrating things in life is a slow computer.

Every few years, we buy an expensive new PC and love how fast it starts up, runs programs, and loads web sites. Inevitably, though it starts to slow down, until eventually we are pulling our hair out waiting for it to do routine tasks.

Why is this? It turns out the answer is actually quite simple and you don't even need to be "technical" to understand the causes and solutions.

The good news, it's not the computer hardware that's the problem. In most cases the hardware you have is perfectly capable of being restored to its original glory and kept in fast running condition with minimal effort.

Rather, the problem lies with changes that occur to the PC's software. The 2 most common causes of slowdown (along with easy solutions) are:

Registry errors - the most common problem

Every time you (or your kids) load a program, game or file, your PC's software registery is updated with new instructions needed to operate that item. However, when the item is removed, these instructions usually remain on your PC. Every time you run your computer it tries to execute these instructions but, because the related program can't be found, it causes a registry error. Your PC is doing a lot more work than it should be and the result is a significantly slower computer.

One of the best ways to manage this is with a neat little tool from a Seattle based company called the Advanced Registry Optimizer 2010 (ARO for short). This program scans, identifies and fixes registry errors - resulting in a computer that's a lot more like it was when you first bought it. On top of the amazing results it offers, it's so easy to install and use that it was recently awarded a coveted 4.5 star rating (out of 5) by CNET's editorial staff.

You can now get a free working version of the software which will quickly scan your entire PC and identify all of the registry errors that may be bogging it down. The free version eliminates the first 100 errors and if you have more errors that you want to clean-up or want to set the program to run on a regular basis (recommended) you can easily upgrade to the full version for just $29.95. After that registry errors will no longer be a problem.

To get the free version simply click here.

Spyware and viruses

Spyware and viruses are software programs that are loaded on your computer without your knowledge or permission. They have various purposes, including:

Changing the default search engine in your browser
Tracking your web surfing habits and showing you targeted advertising
Using your email program to send out spam to other email addresses
Stealing your personal information

Most spyware and viruses get onto our computers through files that we download from the internet or as attachments to emails. They tend to take up a lot of computing power and as a result will significantly slow down the computer.

The simple rule of thumb to follow is to never download any free software programs from companies you do not know and trust, especially screensavers, emoticons and the like. In addition, you should never open any attachment to an email unless you are 100% certain you know and trust the sender. In addition, make sure you have a good anti-virus / spyware removal software running at all times.

Follow the above advice and your PC should stay fast and safe.