If you look at some job titles on Stack Overflow Jobs you can come across several abbreviations: H/F, M/F, M/W. It does not look programming specific (excuse me if I'm wrong). E.g.:
Ruby-on-Rails or AngularJS developer for Open Source project (m/f)
Senior PHP Developer (m/f)
PHP Softwareentwickler (m/w)
Team Leader Web .Net (H/F)
What is their meaning?