Problem: "We don't think "http://localhost/files/" is an absolute path for your data directory"

I'm trying to install elgg 2.3.9 and I get the above message while on step 4. Configure Site...does anyone know how I could possible fix the problem?  thanks in advance!

Beginning Developers

Beginning Developers

This space is for newcomers, who wish to build a new plugin or to customize an existing one to their liking