Fixing the tab order is a rather simple affair. To start, click the top-most text input to select it as shown:

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Next, set the tabindex property to the first value in the order as shown:

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Then repeat for each one of the input spaces using 1 for the second from the top, and 2 for the third. When finished, the tab order should be set to flow like this:

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Note that when setting the tab order in Expression Web, the tabindex property is not changed for inputs with the same tabindex value, so the tabindex property must be set manually for each input to a unique value in order to avoid problems.