For .html and .asp, the answer is yes they can co-exist. I dunno about php.
If you like, you can configure IIS to handle the .htm or .html extension just like the .asp extension. In other words, it can have scripts in it. I recommend that the server be Win 2000/IIS 5.0 for this, though, for performance reasons.
To do this:
To configure IIS to process .htm files allowing scripts:
1 Start up Internet Service Manager 2 Select the web site you want to do the processing on 3 Right click on it and select Properties 4 Select Home Directory 5 If necessary, create an application 6 Press Configuration 7 Select .asp and press Edit 8 Copy down the information in the dialog 9 Press Cancel 10 Press Add 11 Use the file extension .htm, use all the other information that you copied down in step 8 12 Press OK to all the dialogs 13 Restart IIS for good measure
So then Xoc, if it's on virtual hosting where there's no control over the server, it would depend on how they're set up and what they allow, right?
I'm looking at a site that's all asp, which the current pages other than the index page need to be, but it needs a few html pages added for text content. Or maybe the text pages could also be asp - I don't know if that makes a difference to the search engines. I assume it would. Right now there are no other pages indexed at Google other than the index page.
If you need to put PHP code into HTML documents, for example if you are using something like PHPsecurepages to password protect your files, you must make sure that the .htm/.html documents are parsed by the PHP engine.
If you're familiar with .htaccess, you can get the webserver to parse certain directories through the php engine. Otherwise you'll really slow the webserver down if you parse all documents through php.