dbuschho, I am using wforms library and I found the error ..... :$ ..... missing space between validate-custom and the /reg_exp/ so, the correct is: <input type="file" size="50" name="archivos[]" class="validate-custom /\.(jpg|JPG|jpeg|JPEG)/"/>
I'm using Ubuntu Feisty and Firefox.
Another thing... If I don't want to upload a file, automatically takes it as required (because it doesn't ends in jpg) displaying me the current error, so changing the reg_exp as: class="validate-custom /(^|\.jpg)$/i"
We would be indicating that there is a string and it's ending in jpg. NOTE: /i <- case sensitive