The basic difference is that quiet can mean little or no noise, but silent means ZERO noise. If you describe somebody as quiet, it means that person doesn't talk very much. People can also talk quietly (with a very low volume) but itís impossible to talk silently!
I never release a website before asking for feedback it is just in the manual. Always ask the others experts or not about their opinion on how your site looks. It is really important to know what the others think, especially because after hours and hours of looking and analyzing your portfolio, you do not notice the small details anymore and this is crucial. Never release a website before asking people for opinions.