Output an empty alt tag for an image in with views? I have an image field in a view. How can I output empty alt text for the image. 

(For decorative images this is the correct markup 
http://www.w3schools.com/tags/att_img_alt.asp )
If you have disallowed the "alt" text in your field configuration, the system will output and empty value as you want. But if the field has a value in the attribute, you could modify it with hook_preprocces_field().