popup Javascript alert - accessible?

Hi,

I'm doing an audit of a site that uses Javascript to check that forms have
been filled in properly. If required information is missing from the form a
Javascript alert message appears (in it's own dialog box). Is this an
accessibility problem for people using screen reading technology - or are
dialog boxes easily recognised and dealt with by the software and the user?

Thanks,
Jim 

-- 
Jim Byrne Project Director, The Making Connections Unit, Glasgow Caledonian
University, Glasgow G4 OBA, 0141 331 3893

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