*C级IP地址检查:*：对链接伙伴进行IP地址分布检查，而不至于被同一类IP地址的链接所惩罚。
 27. Class C Checker - Webrank Info
<http://www.webrankinfo.com/english/tools/class-c-checker.php>  28. Class C
Checker - Webmaster
Toolkit<http://www.webmaster-toolkit.com/class-c-checker.shtml>
29. Class C Checker - SEO
Chat<http://www.seochat.com/seo-tools/class-c-checker/>

*蜘蛛模拟器*：可以获知网页外观与搜索引擎蜘蛛索引的区别。
 30. Spider Simulator - SEO
Chat<http://www.seochat.com/seo-tools/spider-simulator/>
31. Spider View - Iwebtool <http://www.iwebtool.com/spider_view>  32. Search
Engine Spider Simulator - Anownsite
<http://www.anownsite.com/webmaster-resources/search-engine-spider-sim...>
33. SE Bot Simulator - XML
Sitemaps<http://www.xml-sitemaps.com/se-bot-simulator.html>
34. SE Spider - LinkVendor<http://www.linkvendor.com/seo-tools/se-spider.html>

第三部分：可用性工具

*浏览器分辨率测试*：在不同屏幕分辨率、不同操作系统、不同浏览器下网页的显示效果。
 35. Browser Screen Resolution Checker -
Markhorrell<http://www.markhorrell.com/tools/browser.html>
36. Screen Size Tester - AnyBrowser
<http://www.anybrowser.com/ScreenSizeTest.html>  37. Screen Resolution
Checker - AndyLangTon<http://andylangton.co.uk/stuff/screen-resolution-checker>

*HTML及CSS验证*：毫无疑问,W3C的验证会让你取得更好的搜索引擎排名加分，赶快改正那些错误及不规范的代码吧。
 38. W3C Validator <http://validator.w3.org/>  39. WDG HTML Validator - Web
Design Group <http://www.htmlhelp.com/tools/validator/>  40. CSE HTML
Validator Lite <http://onlinewebcheck.com/>  41. Validation Services for
your HTML / XHTML / WML - Validome <http://www.validome.org/>  42. CSS
Validator - Jigsaw <http://jigsaw.w3.org/css-validator/>

*FireFox扩展*：更多可参考我之前写过的火狐SEO扩展 <http://www.kseo.cn/post/53.html>。
 43. W3C Validator <http://validator.w3.org/>  44. WDG HTML Validator - Web
Design Group <http://www.htmlhelp.com/tools/validator/>  45. CSE HTML
Validator Lite <http://onlinewebcheck.com/>

*页面速度测试*：页面小、下载速度快的网页谁深受用户喜欢。
 46. Speed Tester -
LinkVendor<http://www.linkvendor.com/seo-tools/speedtester.html>
47. Website Speed Test - Web Hosting Top
<http://www.web-hosting-top.com/web-hosting/tools.website-speed-test>
48. Website
Speed Test - Iwebtool <http://www.iwebtool.com/speed_test>  49. Speed test -
WebSite Goodies <http://www.websitegoodies.com/tools/speed-test.php>  50. Web
Page Speed Report<http://www.websiteoptimization.com/services/analyze/wso.php>

第四部分：其他SEO工具

*PageRank预测*：包括未来预测及当前PR值。
 51. Future PageRank - SEO
Chat<http://www.seochat.com/seo-tools/future-pagerank/>
52. Predict PageRank - Page Rank Prediction