When it comes to managing your investments, the mantra of most financial advisers is: "Diversify!"

But deciding where to put your money can be a daunting task. Whether you are a novice investor or a pro, there are a variety of tools on the Internet that purport to help you determine how to best invest your assets for the future.

These asset allocators can be found on numerous Web sites, from those run by mutual-fund companies and brokerage firms to professional organizations, publications and special interest groups. But the $64,000 question (more than that, really) is: Are the sites worth using?

We scanned the Web and test-drove a host of sites to answer that question. (See

Online Asset Allocators table

at end of this story.) Then, we huddled with a real flesh-and-blood financial planner, Ron Roge, for further insight on the risks and rewards of asset-allocation planning in cyberspace. This article lists which asset-allocation sites we thought were the best on the Web. There are more sites out there, but many were either too rudimentary or, like FinancialEngines.com, they charged a fee. We focused on free sites.

Here are the sites we examined:

  • Vanguard Online Planner
  • Fidelity Asset Allocation Planner
  • FinPortfolio.com
  • whatifi.com
  • SmartMoney.com
  • iVillage.com

Some of the sites include calculators or planners, which tell you how much money you'll need to save to reach a specific goal. The sites run the gamut in complexity from simply asking a few questions to essentially filling out your tax return. And the results range widely as well -- from a single pie chart labeled stocks, bonds and cash to a detailed cash flow analysis spanning decades.

In an effort to determine which sites were worth their salt, we put them to the test. We invented an imaginary couple in their late 20s -- Barbie and Ken, naturally -- with two young children, Skipper and P.J., to put through college.

Both parents work and have a joint income of $95,000 (Barbie earns $40,000 and Ken $55,000). They own a $300,000 home with 10% equity and a 25-year mortgage. They plan to retire when they're 65 and have a total of $38,000 in 401(k) plans and IRAs. Ken will put 10% of his income into his 401(k) with an employer match of 5%. Barbie will contribute 5% to hers, which her employer will also match.

In addition, they will each contribute $2,000 per year to Roth IRAs. They plan to save $1,000 per year per child for college, and each child has an existing college fund of $5,000. The couple have an optimistic outlook on the economy, and they are comfortable with a fair amount of risk in their portfolio.

One of the difficulties in comparing the outcomes of this scenario was that none of the Web sites asked for precisely the same information. Vanguard.com's allocator, for example, allows you to factor all your savings goals, such as college planning, home buying and retirement into a single spreadsheet. The rest require you to complete a separate worksheet for each savings goal. All ask questions to determine how much risk you as an investor would be comfortable with, and a few require your broader economic outlook.

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Vanguard.com asks for detailed income and expense information (this will also give you a cash flow analysis, which is very helpful). Others use more general information or focus more on your investment goals. FinPortfolio.com and FinancialEngines.com (both of which offer financial advice for a fee) allow you to enter your actual holdings (e.g., specific mutual funds, stocks and bonds) and calculate expected returns based on this input.

So what do we make of the results?

Enter Ron Roge of R.W. Roge in Bohemia, N.Y. He warns that in evaluating the advice you're given by an asset allocator tool or by a financial adviser, it's crucial to know what the assumptions are going into the model and how the results are being calculated. (Most of the allocators have this information, but it's often buried.)

A forecast may change dramatically by using an inflation rate or interest rate that differs by just 1 percentage point. We noticed several of the asset allocators we used have a default inflation rate of 3% -- Roge recommends using 4%, the historical average. Another vital estimate is how much income you'll need in your retirement. Again, most of the allocators suggested a minimum of 70% of your current income. But Roge argues this will probably be too little for most retirees.

Although common wisdom assumes your expenses will go down in retirement (your children will probably be through college; your mortgage may be paid off), Roge says the investment distributions through retirement can bear a heavy tax burden. While Roth IRAs are a tax-free investment, it's easy to forget that money in tax-deferred accounts is taxable when you withdraw it in retirement. And there are capital gains to consider as well. This is why he feels having a year-by-year cash-flow analysis (up to the age of 90) is so important.

Our real-life financial adviser agrees with the advice given by most of the allocation tools: It's important to regularly re-evaluate your portfolio and make the necessary adjustments to your savings level or your portfolio allocations should your situation change or if your allocations get out of balance. Roge recommends going through this exercise once or twice a year. While minor imbalances can be ignored for a quarter or two, he recommends adjusting your investments once a particular sector gets out of balance by 10% or more.

One final note

: An important factor in planning for retirement is determining how much

Social Security

you expect to receive. Even though we input the same age, income and retirement age into each of the asset allocators, we got vastly differing estimates from the different sites. Our advice: Contact Social Security and ask for an estimate of your benefits, then manually input this number into any of the allocators you use.

In sum, these Web-based asset allocators are a good starting place when you're considering how to manage your money to realize your goals. But they're only as accurate as the information you enter (it's easy to make a mistake) and are clearly not going to give you the kind of individualized advice that an experienced professional will.

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