Here are the sites list for quick check on your web application -
- To check coding standards - http://validator.w3.org/ - Does w3c validation on coding standards.
- To communicate design issues - Fireshot - useful if you want to convey any design changes on the screen.
- Link Checker - http://home.snafu.de/tilman/xenulink.html - checks for broken links in Website.
- For regression test and performance test - iMacros - Firefox Add-on - useful for automating tests. Also measures response time.
- Spell Checker - http://orangoo.com/spell/
- Browser Compatability check - http://www.netmechanic.com/cobrands/MarketingTips/compat_check.htm