If you are talking about phones:
It depends has your operator freezed it up or is your phone "operator free". If its latter, u can do it from browsing settings
Server side:
You should check it from your servers user manual.
Lets assumption what all phone an 'operator free'. I know how to change WAP home page via OTA-settings, but my question is how to change it via WAP-page - like make this page my homepage.
Server side:
I dont understand how server side may be linked in this case.