One thing I run into a lot are files being sent to me with spaces in the file name (this seems to happen most often with images and pdf files). On your local computer this may be fine, but once its uploaded to the Internet you would be surprised to know that many people won’t be able to view it!

This is because many servers don’t know how to read a space (ever seen %20 in place of the space in your filename? Its the server’s way of handling the space) and so instead of viewing your file they will get the dreaded “Page/File cannot be found” error. So rule of thumb? Don’t put spaces in your file names!