Module development and code questions

Hi everyone,
I hope you can help me to solve this headache problem. I tried to figured out the whole day and read a lot of documents, but I couldn't figured out.

After enabled modules such as Filemanager, form_mail, and video, I got an error that form_textfield() is not defined.

Fatal error: Call to undefined function: form_textfield() in /home/up4fun/public_html/modules/filemanager.module

Thank you for anyhelp.

Can anyone point me in the right direction? I'm trying to create a form with the drupal_get_form function, and I get an empty window every time I try to run the following PHP page:

Hi all. I am a newbie here and recently written a module.

I've tried to put it inside the website we are developing and when we add the module inside, it will set the permission of anonymous users such that it can't access the content. I tried setting it again in the access control but when i save permission, it doesn't reflect.

why is this so?

thank you very much! :)

I'm using the book review module, which is functioning fine except for the teaser. I want the book cover thumbnail to display in the teaser. I've got the excert, image, and image assist modules all installed. When I try to add an image to the the excert, it will work up to the point I hit preview or submit. Then, the img & div tags are removed. I've tried a couple of variations of this, but nothing seems to be helping. Any advice?

Thanks!

What's the proper way to include a custom stylesheet in a module?

Acidfree does it like this:

Font size module doesn't validate. This is the error I'm getting:

there is no attribute "language".

script language="JavaScript" src="modules/fontsize/styleswitcher.js" type="text