Mod_speling is a module for the Apache Web Server. Its purpose is to attempt to correct mistaken URLs or various misspellings. It does that by ignoring capitalization. The Linux filesystem is case-sensitive by default, and mod_speling can help you overcome issues with the naming of your files. You may run into such issues when transferring your website over from a Windows-based server, or when publishing website content built on a Windows-based application.
To enable mod_speling, you have to create a .htaccess file (note the dot(".") at the beginning of the file) with the following code in it:
Then save the .htaccess file in the directory where you want mod_speling enabled. Have in mind that .htaccess files work recursively, so it will have effect on all the subdirectories as well.