Rule: Avoid table based layouts
Avoid usage of layout tables. Layout tables are inflexible and less controllable than CSS based html.
The usage of nested tables are general used as layout tables and they indicates a minor knowledge of modern web technologies.
Avoid usage of following tags because they are deprecated, obsolete or were replaced by better semantic ones.
These tags weren't often used in the last few years because the focus of web development are strongly moved to semantic html tags and higher content to tag ratio.
Bad HTML tags are:
font, frame, frameset, noframes, blink, marquee, nobr, applet, basefont, center, dir, isindex, listing, plaintext, s, tt, u, i, b, strike, xmp
Rule: Avoid deep <div> nesting
A deep and often used nested container layout indicates a bad coding style.
Rounded corners or some similar tasks often creates such html code. For most last generation web browsers there are CSS equivalents. Try to use as low as possible HTML elements to increase your content to tag ratio and to lower the page load time which results in an better ranking within search engines.
div, section elemente should not nested deeper than 6 layers.
Rule: Avoid static event handlers
Static and in html tags written event handlers should be avoided and indicates a minor knowledge in modern web technologies.
Another advantage is the reduced byte size an a better caching possibility of the html document.
Bad event handler attributes are:
oncopy, oncut, onpaste, onbeforeunload, onblur, onchange, onclick, oncontextmenu, ondblclick, onfocus, onkeydown, onkeypress, onkeyup, onmousedown, onmousemove, onmouseout, onmouseover, onmouseup, onresize, onscroll
Rule: Avoid low content to HTML tag ratio
A good content to construct ratio is between 6 % and 40 % of the content in modern web pages.
A very low ratio or a very height ratio with a small total byte size indicates a bad coding style. The more content the better possibility for a higher ranking within search engines.
Rule: Avoid Adobe® Flash® usage
Try to avoid Adobe® Flash® elements on the page.
There are several issues with Adobe® Flash®: It is not supported on the most mobile devices, have a bad SEO impact and have big performance issues on Apple® computers (Adobe® Flash® crashs very often).
Rule: Avoid bad navigation structures
A good navigation structur is an essential part of a good ranking in search engines. A bad navigation structure also indicates a minor knowledge of modern web technologies.
void usage of onclick event handler on non navigation related tags
Avoid usage of navigation table constructs
Avoid usage of navigation table constructs because they have a bad impact on SEO and they shows a minor knowledge of modern web technologies.
Tables based navigations are obsolete with introduction of CSS and the widly support in browsers since the year 2001.