Css means "cascading style Sheets" and is usually used for webpages written in html. Xhtml, and xml documents, and can be used to define colors, fonts, and layouts of webpages.
Have you installed, or are you using a free Css editor to convert to XML documents? You have to "run as Administrator" the css parser in Vista or it will give the data error if it tries to run automatically, and is blocked by Vista's UAC.
To get rid of the error, either run it as administrator, delete the css program, or stop it from running at startup. Start>type "msconfig"(without quotations)>click "continue"at prompt>click "startup">uncheck the box for your css editor/program
!!Note!!- cstuff[3].exe may also be a malware/virus program. If you did not install a css editor, or have the cstuff executable, then I suggest you run an antivirus program to scan/clean your system. There are many excellent antimalware programs to choose from on the site, I recommend Eset's NOD32 online scanner/cleaner (NOD32 is a 64-bit antivirus/antimalware program, and I use it on my own computers) .