I recently started setting up an online calendar on a linux server for my school. We paid our 50 bucks, so don't worry

However, my problem is that some catagories in drop down selection boxes don't always apply to the event. When searching, there is the blank feild, but when adding events you are forced to choose one from the list. TO get around this, I added an option which is blank on top, but then this makes two blank selections in the search page.
What should I do to be able to add events which aren't forced to select something (have it blank) from the dropdown box without creating the redundant blank spot in the searching?
Thanks.
Geo