Well.... i use many Language but the preference is as under
1) PHP
Advantages
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- Free, Open Source, Supported by many servers
- Easy to Learn very active developer community
- Cheaper, more reliable web hosting
- a lot of free scripts available
Disadvantages
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- Not as powerfull and rich featured as ASP.NET
2) ASP.NET
advantages
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- very powerful
- ms visual studio makes development faster
- very high support for AJAX
- Silverlight looks promising
Diasdanatges
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- expensive development and hosting
- difficult to learn
- sometimes lacks the performance.
- high skilled coders needed
Rest are ruby on Rails, Perl, Coldfusion i think there is no point comparing these languages with PHP and ASP.NET...
Those who are starting off i will recommend to start with PHP.
Thanks