You may want to check the browser version your using since older browser are not supported. Also, check your plug-ins and try disabling the plug-ins then re-enable one by one to see if it could be a plug-ing or extension causing the issue.
Salesforce Supported browsers:
Salesforce supports all the major browsers but you should not upgrade to the latest browser until Salesforce tests and certifies it first. Here is a link to the SFDC Supported browsers: