Codeswamp is a database of error codes generated from the original sources (e.g. header files) and this page was generated from it. I hope you find it useful.
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Value: 0x800300ff
This table shows the most common 32-bit representations of this value.
Type
Value
Hex
0x800300ff
Signed
2147680511
Unsigned
-2147286785
Matching Symbols
This table lists the symbols that exactly match the value.
Symbol
Description
STG_E_INVALIDFLAG
Invalid flag error.
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Resources
Interested in learning more about COM and HRESULTs? Don Box's excellent book not only guides you on how to implement client and server code, it also gives you a behind-the-scenes understanding of COM, all the way from RPC to DCOM. Definitely a worthy investment for anybody developing or mainintaing software with COM interfaces! Essential COM by Don Box
to search on msdn, 
to search on stackoverflow.