Guidance from 456 Berea Street, Use the label element to make your HTML forms accessible:
All visible form controls except buttons should have an associated label element (buttons are self-labelling). The label element can be associated with its form control either implicitly or explicitly.
An implicit association is created by putting the form control inside the label element, while an explicit association is created by giving the label element a for attribute with the same value as the form control’s id attribute.
iOS does not support Flash. If you want your site to work on mobile devices, replace Flash with HTML5 or at least include an HTML5 fallback to support that ever-growing group of users.
IDs must be unique to an HTML document.
They are harmless, but if you’d like to reduce and clean up your code a bit, you can remove XHTML close tags (” />”) from elements.
The height and width attributes of the element should match the pixel dimensions of the graphic, or the graphic should be resized to match the height and width set in the HTML. If a graphic is bigger than the assigned image attributes, you’re showing the user less than they are downloading. If the graphic is smaller than what is assigned, then the image will scale up and look pixelated. In any case, when web browsers resize images, it does not look ideal.
If a class name you have selected is very similar to an HTML element name, this often indicates that your HTML can be more semantic. Use <footer>I am a footer</footer> instead of <div class=”footer”>I am a footer</div>.
Code such as <h1 class=”largeHeading”>Title</h1> is redundant since h1 means “largeHeading.” A preferable class name would be more specific and indicate how the heading is used. For example, <h1 class=”masthead”>Title</h1>, would indicate both how and where the class is used.
Height and width are not officially required attributes for <img>. However, including them guarantees faster content download. That information also helps the browser determine the viewport space for the image, making page rendering visually smoother.
This is especially important for mobile devices that show customized keypads and widgets for different types.