In Canvas you can check the accessibility of a Page by selecting the Check accessibility icon on the rich text editor toolbar.
Click Edit mode and then select the icon. It will scan your page and identify areas that are not accessible and also provide you with prompts as to how to fix the issues that it finds.
In the following example, the accessibility checker determined that there is a table without a caption.
The checker also enables you to fix the issue, by applying a table caption, and a navigation bar to take you to the next issue: