Exhibit 99.1
 Explanation of Non-GAAP Financial Measures
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    Depreciation and Amortization. Depreciation and amortization expense is a non-cash
expense relating to capital expenditures and intangible assets arising from
acquisitions that are expensed on a straight-line basis over the estimated useful life
of the related assets. We exclude depreciation and amortization expense from Adjusted
EBITDA because we believe that (i) the amount of such expenses in any specific period
may not directly correlate to the underlying performance of our business operations and
(ii) such expenses can vary significantly between periods as a result of new
acquisitions and full amortization of previously acquired tangible and intangible
assets. Accordingly, we believe that this exclusion assists management and investors
in making period-to-period comparisons of operating performance. Investors should note
that the use of tangible and intangible assets contributed to revenue in the periods
presented and will contribute to future revenue generation and should also note that
such expense will recur in future periods.




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    Stock-Based Compensation Expense. Stock-based compensation expense is a non-cash
expense arising from the grant of stock-based awards to employees. We believe that
excluding the effect of stock-based compensation from Adjusted EBITDA assists
management and investors in making period-to-period comparisons in its operating
performance because (i) the amount of such expenses in any specific period may not
directly correlate to the underlying performance of our business operations and (ii)
such expenses can vary significantly between periods as a result of the timing of
grants of new stock-based awards, including grants in connection with acquisitions.
Additionally, we believe that excluding stock-based compensation from Adjusted EBITDA
assists management and investors in making meaningful comparisons between our operating
performance and the operating performance of other companies that may use different
forms of employee compensation or different valuation methodologies for their
stock-based compensation. Investors should note that stock-based compensation is a key
incentive offered to employees whose efforts contributed to the operating results in
the periods presented and are expected to contribute to operating results in future
periods. Investors should also note that such expenses will recur in the future.
    
    Interest Income and Expense.Interest income is associated with the level of
marketable debt securities and other interest bearing accounts in which we invest, as
well as with interest expense arising from our companys capital structure (including
non-cash interest expense relating to our convertible notes). Interest income and
expense varies over time due to a variety of financing transactions and due to
acquisitions and divestitures that we have entered into or may enter into in the
future. We have, in the past, issued convertible debentures, repurchased shares in
cash tender offers and repurchased shares and convertible debentures through other
repurchase transactions, and completed the divestiture of certain businesses. We
exclude interest income and interest expense from Adjusted EBITDA (i) because these
items are not directly attributable to the performance of our business operations and,
accordingly, their exclusion assists management and investors in making
period-to-period comparisons of operating performance and (ii) to assist management and
investors in making comparisons to companies with different capital structures.
Investors should note that interest income and expense will recur in future periods.
    
    Income Tax Provision (Benefit).We maintain a valuation allowance on a portion of
our net deferred tax assets (including our net operating loss carryforwards), the
amount of which may change from quarter to quarter based on factors that are not
directly related to our results for the quarter. The valuation allowance is either
reversed through the statement of operations or additional paid-in capital. The timing
of such reversals has not been consistent and as a result, our income tax expense can
fluctuate significantly from period to period in a manner not directly related to our
operating performance. We exclude the income tax provision (benefit) from Adjusted
EBITDA (i) because we believe that the income tax provision (benefit) is not directly
attributable to the underlying performance of our business operations and, accordingly,
its exclusion assists management and investors in making period-to-period comparisons
of operating performance and (ii) to assist management and investors in making
comparisons to companies with different tax attributes. Investors should note that
income tax provision (benefit) will recur in future periods.
    
    Other Items.We engage in other activities and transactions that can impact our net
income (loss). In recent periods, these other items have included, but were not
limited to: (i) legal expenses relating to the ongoing Department of Justice
investigation; (ii) gain or loss on repurchases and conversions of our convertible
notes; (iii) a reduction of certain sales and use tax contingencies resulting from the
expiration of certain applicable statutes of limitations; and (iv) gain or loss on
investments. We exclude these other items from Adjusted EBITDA because we believe
these activities or transactions are not directly attributable to the performance of
our business operations and, accordingly, their exclusion assists management and
investors in making period-to-period comparisons of operating performance. Investors
should note that some of these other items may recur in future periods.
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