html - IE and Firefox don't load pages -

i'm new web development. wondering if me out simple problem facing. here core problem.

i've developed series of webpage, goes in order.

1. go xxx.com(index page)

2. click on button has a-tag loads next page(inside folder)

<a href="yyy/abc.html"></a> 

this works fine when open page in chrome, firefox , ie not open abc.html file.

what missing here?