Hello.I have decided to leave software programming for web programming and i was wonderin if anybody can tell me with language is better,powerful and can perform a wider variety of task.If i decide to use php,do i need a strong understandin of html?What about coldfusion and java script?Another question is,after the initial codin of a site,how are those fancy interface done eg yahoo.Com,msn etc ?

Of course.If you are going into web programming you need to have
some knowledge of web design:html,css-even if you are not going
to be doing the design yourself and regardless of the scripting language
you choose to use.
What scripting language? Since you have been involved in desktop
software programming,you are probably familiar with Microsoft's
suite of development tools,so migrating to ASP.NET should be a cinch.
It gives you a wide range of languages to choose from;C++,VB,C# etc.
However PHP is highly recommended,it is the most popular scripting
language on the WEB,it is widely and freely available and has a lot of
suppport.