CSS IDs not working when extension is hidden

I developed my site with extensions visible, but when I finished and wanted to make it to production. Now I did a htaccess to hide extensions and add a trailing slash, when people click on a button which redirects/links to #tab1, the url becomes: http://ift.tt/1FHzXSQ

And the CSS ID doesn't open up (the tab).

Is there a way to fix this?

Thanks in advance