Sometimes you might preview a document and the image won't appear, or the entire body of text appears as a hypertext link, or it's all in boldface, or part of the page is missing altogether.
The more you work with HTML files, you'll find that typographical errors cause
most of the problems you might encounter.
For example, leaving out the ending </b> tag for bold or the </a> for
a hypertext link might make the rest of the document, respectively, bold or
look like a single giant hypertext link. Leaving out quotation marks might
cause part of a sentence to become chopped off; misspelling the name of an
image will cause it to not appear. Similarly, a misspelled filename, or an
incorrect upper or lowercase letter in a filename, could also cause
a browser to not connect a link properly.
Whenever you have problems, go back to your source file and check your typing and make sure all your HTML tags are correct.