The most common WordPress mistake I see is:
When you add an image to a page or post, you do not want it to link to itself, you simply want to embed it in the page. Unfortunately, the default setting in WordPress is to have your image link to its own media file when you insert it into the editor.
What does that look like?
Here is an image that links to its own media file:
This is caused by the way an image is inserted into the page. After you upload an image to the media library, you are given the choice to “Link To” something. This defaults to “Media File”, which is what you see above. You don’t want to put images in a page like that, do you?
How to Fix It
Instead of linking to the media file, simply change the drop down to: None (as seen below)
This results in an image on your page, that does not link to itself:
Make sure you are not making the same mistake when you add images!