One of my favourite examples of what not to do in a technical presentation is the application developer who includes lines of code in their PowerPoint slides! What benefit is there in displaying lines of code on the screen? Unless you are showing something VERY specific that needs that level of detail there is nothing to be gained by displaying such detail. Your audience will not have the ability (or interest) to decipher the detail they are being bombarded with.
With everything you display on the screen ask yourself “What would I lose by not having the audience see this?” If the answer is “My audience won’t understand what I’m talking about” then keep the slide. However if it is any other answer – dump the slide – you will only confuse or bore your audience!