In order to make consistent, neat and tidy looking website it is important to use grid to devide section of the content. grid based design is basically structuring website with html columns and rows in order to place images and text firstplace before you apply css.
There are various devices with different screen sizes now days and if responsive design is not applied to coding the website could get cut off when the screen gets smaller or the content could misplace when the screen size is stretched. Responsive design will allow the contents to stretch automatically and shrink depending on the size of the user's device and also this will be always centered so it is handy for users as well. media queries definetely benefits users but also the developer as well.
there are semantic tags such as h1-h4, img, form. I think using right tags and right semantic structure helps users to understand the website better. For instance it wouldn't be good if h1 (usually used for heading) is underneath the page and h4 (which is smaller size than h1) is placed at the top of the page as title. Semantic structure is basically a structure that helps users to understand website better by using the code correctly at the right place.
Not at the moment..!