Why should you avoid adding spaces in an <img> tag?

Adding spaces within an <img> tag can lead to rendering issues in XHTML, where whitespace is considered significant. In this context, XHTML is more stringent than HTML regarding syntax; it requires closing all tags properly and treats whitespace as relevant. If you inadvertently insert spaces or improper formatting, it could disrupt the correct rendering of the image or potentially cause errors in the way it's displayed on the web page. This can lead to issues such as misalignment or the image not being displayed at all, which directly impacts the user experience.

The other options may have implications that deal with performance or technical aspects; however, they do not specifically address the syntactical issues associated with improper formatting in XHTML. Thus, the focus on how whitespace can disrupt the rendering in XHTML clearly highlights the importance of proper syntax in ensuring images display correctly on web pages.