I am not a marketing guru or an SEO expert, but I am a developer and part of my job as a developer is to code semantically with SEO in mind.
Does valid code improve SEO?
No it doesn’t improver your rank status.
If your code is not valid,
- It can hurt your SEO rank because of semantic issues.
- It simply looks unprofessional.
- It will slow down page loading because the browser switches to Quirks mode to evaluate your code and decide how to display it.
- It can cause display issues with in various browsers.
- The list goes on…………….
Fact is, if your code can not be followed because of being invalid, it will most likely cause issues displaying in browsers, being read by bots /spiders and most likely will have accessibility issues.
Use the tools available, they are there for a reason.
For the employers, do this also, validate the work you payed for, you will not regret it and it will save you money in the long haul.