Create a page and edit its page content. There are three things to test: 1) an image with no alt text. You will need to write this by hand as our image dialogue won't let you create an image with no alt text unless it is marked as being display only. <img src="whatever" /> 2) text with a font color close to the page background color that has been saved. 3) text with a font color close to the page background color that you have just added but not saved. Once you have all of these click on the accessibility checker button and check that all three problems are reported. You should be able to click on text in the problem dialogue, the dialogue will close and the relevant text be highlighted in the editor. When clicking an image in the dialogue, the dialogue will close but it is not obvious that the image is being selected.