How do you express intention (for + gerund English structure) in Chinese?
Since there's no indication of you actually studying Chinese, I could just give you the answer by providing the correct Chinese phrase .

However, other users who are actually studying Chinese can benefit from a more detailed answer.  I would make here.

In English, the grammar structure of "a proposal for creating a website" is:
"A" (classifier) + " proposal" (noun) + "for creating a website" (adjective phrase) 

A word for word translation in Chinese would be 「一個建議，有關創立一個網站的」

The problem is, the  (classifier)+ (noun)+( adjective phrase) structure  is rarely used in Chinese grammar; 

We use (classifier) + (adjective phrase) +(noun) structure in Chinese instead. So the sentence should be 「一個(有關創立一個網站的)建議」


「的」 in 「有關創立一個網站的」is needed to indicate「有關創立一個網站」 is a adjective phrase, (the same rule apply to adjective clause, relative phrase and relative clause)