Please check this article if this will help you fix the problem:

http://support.quickbooks.intuit.com/support/Articles/HOW13289

Resolution for 'Appearence issue: 'QB 2014 font suddenly very small' available: Yes.

The Appearence issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the Appearence issue yourself by looking for a resolution described in the article. If it is a complex Appearence issue or you are unable to solve the issue, you may contact us by clicking here or by using other Appearence support options.

For more information about resolving issues related to Appearence in Quickbooks/QBO or to get support for the issue 'QB 2014 font suddenly very small', click the link below: