Crash signatures ^{( what's this? )}: nsStyleSet::FileRules(int (*)(nsIStyleRuleProcessor*, void*), RuleProcessorData*), nsStyleSet::FileRules(int (*)(nsIStyleRuleProcessor*, void*), RuleProcessorData*, nsRuleWalker*)

This type of crash is often caused by:

• The My Web Search Toolbar: See How to uninstall the My Web search toolbar.
• Malicious software: For steps to take to resolve problems with malware and Firefox, see Is my Firefox problem a result of malware.

For troubleshooting other types of Firefox crashes, see Firefox crashes.